[b-man]

Two good reasons to crack it open.

Worn cam lobes are pretty common, usually at least a couple have rounded off to the point where there’s a significant power loss.

Stretched timing chain, another power loss.

Once you freshen up these two things it will feel almost like a new engine.

I’d stick a new 066 cam/lifters and timing set in it, while you’re doing that you can check out the timing cover and see if it’s getting corroded and replace the water pump, divider plate and sleeves. Use the 068 cam instead if you really are doing the swap to 3.23 gears in the near future, I would also recommend a 2500 stall converter with the 068 cam.

Keep the log exhaust manifolds. Very little bang for the buck spending $500 to replace them with HO/Ram Air manifolds and head pipes for the 5 to 8 horsepower gain at most at this power level. Just use some PYPES 2-1/2” head pipes and a free flowing exhaust. Keep in mind that the 326, 350, 400, 428 and 455 all share the same log manifolds, so a 350 breathes pretty freely through them compared to their bigger brothers that also do just fine with them.