Most truck headers are designed for a D2TE-AA, C8AE-H, or a few other low port heads. So I'd likely stick with the 360 heads. Most FE heads will work, but you need to talk casting numbers, because in many cases, 360 are 390 are 428 heads.
A modern multi-angle valve job, 45 degree seats, and a bowl blend will do wonders and do just fine with headers and your iron intake.
I'd prefer long tubes if you are willing, and a 2.5 inch exhaust with good performing mufflers and a H pipe, do the head cleanup, and your 4 barrel 600 and you are running pretty well on the cheap. I forget when the F100s went to throttle cable, but if 75 is still mechanical linkage, make sure you are getting full throttle after the swap
Next would be a distributor recurve, and it'd run pretty well.
After that, I'd likely go inside and add some cubes. 390, 416, etc, but they can run real well with just the changes listed.