68-70 Manifolds on 72 340?

domdart said
It has a 3.55 in it. I just ordered a sure-trac II for my 3.23. I want less rpms and less exhaust noise.

I understand where you are coming from. I got tired of the noise and drone as well. Do the exhaust first. I did and stayed with my 3.55 gear. Also If it is an automatic the correct converter stall helps a lot as too.