1 5/8 headers

wish I knew. Couple guys that have forgotten more than I know said 25-30 horse perhaps. Dwayne was one of them
not sure what that is on a time slip.
only other thing I am doing is freshening trans, and changing flash on vert( hoping I am going the right way on that)..lol
decided not to swap to 1.6 intake rockers

If it picks up 25hp, it should run in the 10.50-10.55 range.

Stock 340 A cars with the same gear as a 383 B body would eat that B body. 440 and Hemi cars, not so much.