I developed the same kind of trouble with my 55.1 p/u when I was stationed at Tinker, OK in late 80s. Drive about 10 miles, would sputter, backfire and die. Sit on roadside about 30 minutes and could start it up, 5-10 miles, same thing. After 2 or 3 times of going thru this crap (was actually going leave it on roadside) remembered that I had the same trouble with an old AF '62 trashnational semi I used to drive to Gila Bend, AZ back in the later 70s. Replaced the metal fuel line with a rubber one on my p/u and never had vapor lock again. Not saying that's what is wrong with yours but if it is.......
S2
