funny? when I was starting out working on cars I always thougt the engine block was a 'dumb' peice of iron, but there is a great deal to learn from cutting away the core and finding out its secrets before a build
The GM auto trans plate overlaps the 6G72 v-6 bolt pattern very nicely. because I can cast my adapters, I am not dictated to by a standard adapter plate thickness size, I can adjust to any thickness I need
I started to think about starter spacing and this will lend itself to the selection of flywheel size
then I turned my attention to the coupler design, the first thing to do was to find all the critical demensions of the exiting crankshaft
I cut up the crankshaft too >;o)
I laid out a couple differnt size flywheels just to see what would interfer or what had a better fitmant so I could make the best choices during the design
In the rough draft, the coupler is a no comprimise peice of hardware, there can be no failure at this piont, any comprimise in this unit will be made elsewhere in the design, the thickness of this unit will dicate the thickness of the adapter plate
I know, it aint a computer drawing, but I spend hours just drawing and erasing and drawing thicknesses, shaving 1mm here and adding an angle there and keeping it strong and keeping it light and trying this and that , just hours of thought and frustration >;o) making a complex peice simple is what I enjoy doing
How many bolts does the 6g72 crank that you have your hands on have Bill? For some reason, I am thinking the na cranks were 6 bolts and the turbo cranks were 8 bolts. I will have to look into this, I love the idea of a 3.0 or 3.5 swap 
