I'm with you Joker. I think it might be electrical as well. Your problem bert sounds just like the problem I had that I mentioned in my first post above. I would take a good look at your distributor, coil, condensor, etc.

1960 Chevy Apache 1/2-ton
1965 Chevy Half-Ton Suburban
1966 Chevy C60 2-Ton

Stupid is as stupid does. - Forrest Gump