I recently picked up an 81 300SD which doesn't run because of an over heated engine. A local yard has offered me a running engine out of a wrecked 83 300SD. The engines seem to somewhat different. Most noticeably, the turbo seems to be positioned somewhat lower on one of them. I would appreciate any opinions on the quality of the two engines (the original engine may be rebuildable as an option). Also, would there be any major difficulties in installing the 83 engine in the 81 body?
My thanks to anyone who can contribute here.

Richard