Exhaust manifold hitting steering pump

Hey, I recently took out my headers that I have on my 70 duster 360. I bought a pair of 340 exhaust manifolds from what I think is a 68 dart. When I installed them, I couldn't get the the driverside on, so I had to jack up the engine to get it on. The problem I have now is that once I lower the engine back down, the manifold sits on the power steering pump and it also won't lower all the way down onto the engine mount. I decided I could try to shim the motor mount, but I wasn't sure if that is a good idea. Has anyone else encountered and issue like this before and if so what was your solution? Do you guys think shimming the motor is a bad idea? Thanks for any help and support