I am not an expert but I did rewire the tail lights in a 67 that someone had just cut (GASP!) all the wires and just hard wired an aftermarket flasher up to it so all the lights flashed. How bad is it? A wiring manual from Jim Osborne really helped me a lot. Also, check out cougars unlimited. they have parts. even new electronic replacements for the sequential unit. Good Luck
The sequential motors on both our cougars have been removed, I see on the 70 they connected the wiring up using the side markers, I had to do it myself on the 72 and finally got it to work, I now have the middle bulb working as a brake light and the other two working as indicators, all 3 bulbs work as taillights. Naturally just after I cut the wiring in the loom before it got to the whole sequential thing we met the previous, previous owner who told us he has the sequential motor at home and we must just come fetch it...go figure. So a small warning, don't cut the whole thing off unless you are totally sure that you are not going to get a sequential motor/unit in the future. There is a site that explains the entire working of the lights, if you follow their wiring colours it should be easy enough to wire up the brake lights.