Bob
When I build a chassis( for Pro Stocker or street rod) I set up a nine inch rear with a length of heavy wall tube (2.750x.750) that goes thru the main bearing saddles of the mock up engine---this gives me the driveline centerline, I set the high of the crank pulley,
oil pan and probably the most restrictive objech being the scattershield lower flange. all this is set relative to ground level---it is then pretty much an absolute to build from---
Jerry