I have a 1969 lemans. Supposedly last high performance 350. supposedly heads and cam more high performance? Should I leave as is ?

if that car came with a hi-po engine originally, it would be a 368- that engine doesn't look original- it certainly didn't come with a chrome air cleaner and valve covers- and the manifold looks suspicious- hard to tell from the foto, but I would guess somebody is pulling your leg about the "original 350"

or else you got your terms wrong here- that does look like a big block in the photo- just leave it, and if you want to go fast just buy a new Camaro-

Yeah Some has been added to the original 350, 368? Big block pontiac? Stick to chevys.

The 1969 HO 350 HO was equipped with the 400 cu. in.'s large valve heads (# 48's) and the 400 HO .. If I knew all the answers, I wouldnt be on here asking questions.