Rednate, (and others)
Just a suggestion....mention to your machinist to make sure that he resurfaces the rear main seal area on the crank. Felpro makes a main seal sleeve that will insure your new seal will do it's job.
Also might mention....trying to use the conventional engine hoist inside the cab to lower the sm420 didn't work for me. With the truck up on stands you don't have enough interior room to do much more than just support it. I wound up making a little 2x4 box frame (2x4's on edge) which surrounded the transmission cover area and with an old boat winch mounted on a 2x4 that spanned the box frame (parallel to the firewall). Made a rope harness for the transmission. Worked like a charm to support and slide the sm420 to the rear to clear the bellhousing. Used some vise-grips in place of the winch handle which let me (I'm a 1 man crew) lower it down while laying under the truck. I think I have some pics in my Webshots album. Hope this helps.
Dave