This thread was a great help to me, I ended up going the route of the Hedman headers, shorty plugs, and paint for my 1978 G30 Ambulance project.
I noticed a performance increase (judging from the seat of my pants lol).
My favorite part is the sound, Nothing beats a big block withe headers!
Anyway, I filmed the whole thing so if links work here (sorry I am new) you can see how I did it.
Its a 3 part video, I posted the last part here because its the most interesting but the others are out there if you need them
Hope someone finds this helpful!https://youtu.be/C2uqP5ij9kU
If the link doesn't work, just look for the YouTube channel: JeepSheepTV