AMD is your best bet for metal. That's the route for aftermarket tin I would go. Don't expect a perfect match/fit. In one way or another fresh panels will need tweeking to make them work. Check out my thread, Detmatts, Donny's GTX, SGT's and a few other threads. With major AMD metal placement, that will give you a real good idea what i'm talking about when it comes to dealing with aftermarket panels. When I mentioned OEM, I did not mean go down to Dodge and try to order some. That would lead to you getting laughed out of the place and a conversation piece for the parts counter guy for the next two years. I was refering to patching and trying to leave as much original (OEM) metal in place as you can. OEM metal out of a donor/parts car works well (ask the pre-'68 guys), but good floor pans or trunk pans out of them, well...good luck.
Here's where I can see justifying a patch. Every so often we see guys come on here with a project and being new to the world of restoration, unfortunately they have no concept of what they're up against. The time/money/equipment/facility to achieve major autobody goals is staggering. They start by blowing 2-3K in AMD panels and tearing the car apart. Before too long it becomes very apparent they bit off more than can chew. One panel off lead to another bad one, then another and it becomes a runaway train. Your one month project just turned into months worth of work and 2-3K is now 5. Here comes in the time/money/equipment/facility factor as well as frustration because of not having the know how or immediate resources to engage issues. So the car sits for a month, then another then another. After awhile the car becomes a thorn in the side and ends up on craigslist, along with a pissed off old lady and a billfold full of tumbleweeds. This is reality. I'm not saying in that senario, they all turn out like that, but flip a coin.
Your car "looks" pretty solid....You don't have a lot of experience under your belt and sounds like you're a bit younger (thus, possibly don't have major funds, tools, equip, facility and have constraints like a younger family to contend with or something along those lines). As long as you patch out to good metal I don't see the issue. It will be cheaper, quicker, require less work and less skill. Yup, down the road panels will need to be changed, who knows how long, but even the guys that blast and go for the full rostisserrie have rust in between the pinched panels that will eventualy bubble out and need to be changed. Like I said, where does the maddness end? Unless you completley disassemble every panel off the car, you'll never get all the rust, and even after that, the process starts all over again. It's just the way it is.
So, you're not going to be visiting every local car show on lazy sundays, you're not tearing the car down for a full resto, you wanna be on the road. Do you take the leap and tear into it or isolate what you got and move for a full resto a bit down the road? That's the question you'll have to figure out on your own. Like mentioned earlier, check out the restoration threads. That will give you a real good look of what it takes and where your project can lead. Lotta guys here with a lot of experience that are always willing to help when the need arises. Learn what others have had to do. Take a look at the work, experience, time, money involved and think about where you and your plymouth would fit into a senario like that. Either way....patches or panels, we'll be here to help.