GM Bellhousing Bolt Patterns
that web site has the bolt pattern, then you need to buy a piece of 1/8" aluminum, get the pattern transfered to the aluminum, drill nessasary holes, finding the input shaft center, another set of holes for bolting the motor to the adapter, a coupler for motor to transmission. and that's more the leave it in gear and forget it(allowing the motor to spin the car up to speed)
ps. if that doesn't help look up "60 degree v6 bellhousing pattern"