The Holley Terminator X Max system is a drive by wire (DRW) system so you will need a pedal, however they are easy to come by from places like Rock Auto. The one I bought is for a 2015 Jeep Cherokee which was recommended by another member here. You can I believe convert to a drive by cable but do your research.
You can use any small block Mopar trans, many opt for one of the newer transmissions because they want the OD which allows them to run deeper gears for around town and racing fun, however there is nothing wrong with a 3 speed 727 either, just depends on what you want and intend to do with the car.
Holley (as i think you have discovered) makes a lot of the parts you need, however you have to do your research well to keep from spending money needlessly but even with research you are bound to run into an issue or 2.
Swapping in a G3 Hemi is not magic, many have and are doing it. The main things you need to look are;
- Engine: there are a number of choices here, pre 09 5.7, post 09 5.7, 6.1, 6.4 or even the 6.2 Hellcat. If you are going to do this on a limited budget, pre 09 5.7's are the cheapest. Then you need to decide if you want a truck engine or a car engine which really has to do with the intakes and the serpentine systems (both of which can be replaced as needed). Whatever engine you select you are going to need motor mounts (Holley, TTI, Ram Man, Bouchillon, etc.). My advice here is to get mounts that are designed to work with the headers you intend to use. Also you are going to need a new oil pan, again Holley, Kevko, Milodon, etc. I prefer the Holley unit because it is cast aluminum and less prone to bending along the mounting rail and is a bit more durable in terms of damage from scraping or road debris, also it uses the stock gasket. Lastly you need to look at where all of the accessories mount or probably better said what accessories you want to use (power steering and AC specifically). This will/can affect which serpentine system you can or will use.
- Electrical system: your car as it sits was never intended to run modern electronics and modern engines require a much higher level of power than the older cars. In stock form most 70's Mopars ran a 60 amp alternator, however modern vehicles today run 120+ amp alternators. Therefore your wiring needs to meet this increase which usually means a new harness at least. Additionally a G3 Hemi will need a unique engine management system (ECU and harness) which can be obtained from a variety of places to include a rewired stock harness out of a modern Mopar, a Mopar Performance system, Holley Terminator X, etc. Which way you go is dependent upon what you want out of it (other than just work) and your level of expertise and comfort with wiring. The Mopar Performance system is basically plug and play but does not offer a lot of tunability (nor does a rewired stock harness), however other systems like the Holley offer a lot of tunability yet are basically plug and play.
- Fuel system: You are going to have to modify or upgrade/replace the fuel system to feed the G3 Hemi. I am not sure if Tanks Inc. has a new tank that will accept an in tank pump or not but if not then you will need to decide what you want to do here. You can run an external pump or use one of the retrofit systems like Holley offers. You are going to need to replace the lines and add EFI rated filters. There is the issue of return lines, some will argue that when set up in a certain configuration you do not need a return line, my belief is that you should run one as it allows the system to circulate the fuel which helps with cooling the in tank pump plus it takes some of the pressure strain off the system. I am sure there are those that will argue this but since you are replacing the lines anyway, adding a return isn't that much of an issue.
- Transmission: I already addressed this but if you were to go to one of the modern AT transmissions then you will need to control the electrical side and there are harnesses that will do this out there that need to be integrated into the system.
- Driveshaft: There are many sources for these and they come in a variety of materials, sizes, etc. You will need to know what size U joints you want to use and then order a shaft to meet this. You should probably wait until you have the engine and trans installed and then measure the length you need. Do not use any charts or internet suggestions on length, measure YOUR car and set up and then get a shaft that meets this. I would bet that you have a drive line shop in your town that would be happy to make you a drive shaft. The upside here is that you can can actually look a human in the eye and explain what you need and when you have an issue you can go back to that human and have a discussion.
- Exhaust: you will most likely be running headers and there are a lot to choose from (Holley, TTI, etc.) but again, do your research and get headers and motor mounts that work together. The rest of the exhaust is like any other car however you will need O2 bungs because you will need to install an O2 sensor (at least 1) for the G3 to operate. Most new "swap" headers offer O2 bungs already installed and your engine management system will probably come with the O2 sensor.
- Cooling: more than likely you are going to replace the radiator, be mindful of where the inlet and outlets are as the G3 Hemis are a bit different than the old school stuff. Also you will most likely will run electric fan/s and this can be a bit of a pain because there are lots of options and not a lot of information. Personally I like factory systems like those offered on the newer challengers. Understand that electric fans draw a lot of power so you will need relays and a good power system.
As for the difference between 72 and 73 I cannot really address that however I built a 73 Cuda and it was/is pretty much the same as it's predecessors. I know that in the B bodies engine mounts changed so that might be an issue but I am sure someone here knows this (
@Nacho-RT74)
This is a swap wroth doing IMO, but it not without it's challenges however it is not all that hard either.
I hope this helps, there is a lot of knowledgeable people here so don't be afraid to ask questions. Start a build thread and post your progress and questions there.
