Installing Headers

If the engine is just setting in the mounts and you can pull it back out it would do that, set the headers in the car and drop the engine back in over them.
I have changed headers on a 74 Duster a few times with the engine and trans in place and it can be a PIA but i have found raise the engine up as far as you can, pull the oil filter adapter and torsion bars, pass side will come in from bottom and drives side from top.