The best way to split the cases and reassemble them is with the factory tools.
The case splitter (pt. # 502 51 61 01) is kinda like a c-clamp with two fingures the slide into the crank case and cradle the crankshaft. The other end just pushes on the crank. If you have any fabrication skills it wouldnt be too hard to make one.
To put it back together you need to use the instalation pullers (pt# for 272 mod. 502 50 30 04). All they are is some threaded bolts that screw on to the crank shaft ends with a spacer that pulls the crank into the case half. Kinda hard to fab unless you have a mill, lathe,and alot of extra time.
This is the quickest,easyiest way I know of. Ive seen people bang away to get these things together and apart and its scares me. There may be OTHER ways that are unknown to me.
GOOD TIP: WHEN YOU ARE INSTALLING THE CRANK BRGS,...HEAT UP THE CASE AND DROP IN THE BRGS. IF THEY DONT JUST DROP IN YOU DIDNT GET THE CASE HOT ENOUGH. THEN PRESS IN THE CRANK.
