could the intake be holding my low end down?

Not that I want one(I don’t), but say...... in the past ten years or so(or whenever the OP’s engine was built)..... where would one have sourced the “correct” stock spec replacement 340 “std trans” cam?
This was a one year only thing, right?
‘68?

Which would lead me to wonder....... I wonder what it really has for a cam in it?
The seller and his dad were pretty heavy into Drag racing- they had a large shop and a small junk yard that was full of A bodies! Lots of parts, so there is no telling. They 'built' this duster for the son when he was in high school but pulled the engine that was in it when it was sold to me (as we agreed on). It was a high compression radical mill that I really didnt need or want- and he ran some 12s with but not on a regular schedule.
In any event, the engine starts and runs fine and has a great sound- its been just what I needed.................