People will argue different but the only way to take it out of a Dodge is out the front. Take the complete front end off then take the intake off and get the chain as low as possible into the intake then jack the van up in the air till you can get a cherry picker in. I pulled my 340 out of my 77 installed main bearings and put it back in in less than 6 hours start to finish.
It doesn't necessarily HAVE to, I have seen it done out the front passenger door but to do that you have to drop the tranny out the bottom first. Also at the factory they changed them out the bottom by dropping the k-frame