I have done this by welding-up some special engine mount brackets.
The job is harder to do if the orginal V-8 is not in the car because I use mark the crank's centerline onto the K-frame before pulling the V-8.
Then it is a matter of installing the replacement SL6 & trans, attaching the rear trans mount and shifting the engine around untill the crank's centerline matches the mark.
I use a level to get the tilt correct, then start cutting cutting and welding the mount brackets.
This photo show a "home-made" mount bracket to fit a SL6 to a V-8 K-frame.
DD
