Classic/Antique Car Repair: 1968 F-100 Stalls, vacuum leaks, strange places

Question
I need your troubleshooting advice. I have a 1968 F-100 pickup, 240 cid manual transmission. The engine starts with normal RPMs, but then drops out to very low RPMs, then back up again until it finally stalls out. The engine starts again but does the same thing. I tried replacing the coil but the engine reacted the same way with the new coil. I need some new ideas to investigate so I can keep the old dog running....thanks!

Answer
Would not have thought coil, sound fuel related to me. Have you tested your fuel pump with a gauge?

Also check for vacuum leaks in strange places (pcv or equivlent, brake booster, a/c damper vacuum horn, etc).

You did not say what happens when you rev it or try driving.