74 Slant 6 Bogs & Stalls Under Load / 30 mph

Dunno, sounds like fuel
Starvation to.me. when your car dies immediately check the bowl for fuel if you have to take it off so be it. I had similar symptoms when my fuel pump went south. It would start and idle just fine, take it for a spin and it would wheeze , lose all power and die. would start up fine in a minute and idle again only to lose power and die again under load. I had an electric pump so my symptoms would be slight different than yours but sounds like fuel to me, and now a dirty carb after it sucked the bottom of the tank. even a new carb can pick up a nugget or two and plug something important