SWEET and I worked through a persistent issue with my truck that had the same symptoms you described. I had trouble with it for almost a year (as I was rebuilding things on the truck). I would have SWORN it was fuel pump/delivery/carb issue.
For me, the bucking only occurred under power, but going up even the slightest of inclines. If that's you too, you may want to look at your timing. SWEET dialed mine in and it stopped the bucking problem.
If fuel-related, which I also experienced, I fixed mine by ditching the Rochester that leaked gas all over my engine (even after two rebuilds) and went with a rebuilt Carter YF from Carb-x. Another bolt-on fix. Still running that great carb.
Best of luck!
Jim
