I like the split loom stuff that comes with the Sniper. Several different diameters available from the usual vendors. You can zip tie it, harness tape it etc.
Here's the wiring in the trunk coming from the fuel pump and sender.
Made a bracket for the Hyperspark ignition box under the battery, you can kind of see it under the battery in the below pic. The box is on the inside, the connector is facing the front. There was not enough room with the power steering hoses occupying the same space. Initially I thought about running it inside but after a lot of back and forth, this seemed like the best place for it. The main ECU B+ wire and ignition box wire are fused right at the battery with inline blade fuse holders. This is a NAPA (labels removed) battery with top and side terminals. Having both top and side terminals turned out to be a good choice, keeps the Sniper connections separated from the main battery cable.
This was an early iteration of the wiring, does not look like this anymore but may give you some ideas.
This is how it ended up. I hate to say it but after so much trial and error, I pretty much gave up on trying to make it look real sanitary. If/when I take the engine out the car, I will re-do it. It's not bad I guess.
In this pic, you can see the B+ junction stud to the lower right of the bulkhead. I run the alternator sense wire to that with a jumper from the starter relay. I'm sure there are better ways of accomplishing this. The coil under the clutch master cylinder reservoir is for a mechanical oil pressure gauge in the dash, it will be gone when I get new gauges.
Hate to say it but unless you have a small block Camaro, the harness Holley provides really leaves a lot to be desired. When I rewired my car, I removed all unnecessary wires and at the same time incorporated the Sniper wiring into the new harness so it didn't stick out. That was a big project for which there was no instructions or guidance.
When incorporating the Sniper into the new harness, I used some empty cavities in the bulkhead connector for the switched 12V wires and the Hyperspark ignition trigger. Inside, these were wrapped into the dash harness and run directly to wherever they needed to terminate.
Basically I wound up re-pinning every single wire in their supplied harness. For example, the fuel pump relay is now under the dash, no way to do that if you just install it the way it comes. On the 10 pin connector I only wound up using two out of the ten wires so I have this giant bulky, connector hanging there with two little wires running out of it, I hate that. My coil is on the passenger side inner fender; with the ignition box under the battery, the supplied coil wires were too short, had to get longer wire and re-pin them to reach across the radiator support. And on and on.
When re-doing all the Sniper stuff I became real familiar with Metri Pack connectors. They were easy to work with. I ordered a bunch of things from EFI Connection, they carry a lot of Holley-specific parts including most of the terminals that are in the Sniper harness.They also have TXL wire which is really nice.
https://www.eficonnection.com/
Not sure if that's what you were looking for but there it is. If I was starting from scratch it would be much neater. I found it really hard to do it the way I envisioned it - there were too many compromises and instances where I had completely scrap an idea and go back to square one. There's only so much you can do with the engine and the dash installed. I will admit the wiring became tedious and I needed it to be done no matter what it looked like.