Magnum Exhaust Manifolds in an A Body

Crap, I was really hoping I could save some money using these manifolds in my '70 Duster but there's no way I'm converting to manual steering. I spent big bucks for the awesome Firm Feel Stage 2 PS box and I'm not about to yank it out... So what other options are there for exhaust manifolds? How do the later 340 manifolds compare to the earlier ones? I found a pair of 1973 340 ones starting at $100 on eBay, decent deal or no?