Anyway you look at it your going to have to do some wiring. I just got through wiring a MSD start/retard box into my ignition tonight.

I mount all my electronics on a 1/4inch thick aluminum plate ( say 24 X 12 ) and I bolt that to the roll bar with tabs welded on for a good ground.

Whatever you do start with a LARGE guage ( I use a welding cable ) main feed wire from the battery to the starter solenoid. I mount this on the plate under the passenger side dash. I then feed a terminal strip with 2 Number 10's in paralell from the large welding cable. ( Good place to stick a main fuse ) I then jump from one terminal to the next about 8 times and make a bank of 12VDC feed wires for each device. They can be labled this way for easy troubleshooting.

I use a Moroso switch panel which is fused from these feeds/terminal strip to each device. ACD also makes a nice switch panel. In my old footbrake car I made my own switch panel out of an electrical Hoffman box 4X4 in size. I even used some of those little DC circuit breakers like on the big trucks, which makes it nice instead of fuses. If you build your own box , buy some 24Vdc indicator bulbs, they aren't as bright as 12Vdc and they still come on with 12Vdc. they just don't blind you.

I wrap all my wire in that automotive spiral wrap, you can buy it at the parts store.

I've done 2 other cars this way and 2 rails. never had a terminal failure yet.