[BADGMC]

You still have the 1.75 headers on that thing? If you do I can tell you it would be a better use of funds to put a set of 2" primary headers on this instead. You'll probably pick up 20-30hp and lose minimal torque. On the dyno my buddy's 454 picked up 30 hp just with that header change. Went from 570@6000 to 602hp @ 6000-6200. Peak torque moved up like 200 rpm to 4900 otherwise there was no significant change. His engine has AFR 265 heads and a Comp XR280 solid roller and vic jr. intake ,otherwise it is similar to yours. Hooker Comp 2455HKR headers (2" primary, 3.5" collector) is what we used on his 80 shortbox. Slight modifications (because of raised exh. port on the AFRs) to make them work and the price was only $165 new and they don't drag on the ground in a lowered truck.

If you're going to keep the rpms below 5000 the 1.75" headers are ok on an engine this size but anything more than that and it's gonna choke. Our dyno guy is Jason Line's (NHRA pro stock driver) brother. It was funny because he laughed about us trying the small headers but it ended up being a good learning experience on how much difference a small investment in certain parts can make.

Oh, and being you have a flat tappet cam in a bbc it's probably going into valve float as well unless you have a lot of seat pressure on the springs. This is very common.