Installing 1972 340 manifolds 3614368 (driver's side) and 3418623 (passenger's side, center dump) - Any Exhaust Pipe Clearance Issues to be Aware of?

Sho nuff. Have you thought about the TTI head pipes? A little pricey, but mandrel bent and they are really nice.
I'll prolly end up having a local muffler shop mandrel-bend the pipes for me. They should also either have in stock or be able to fab up some pipe-to-manifold flanges.