lance345,
It is a little too late for you with your build but for future builders using the MR2 look into widening the entire chassis. Nobody thinks twice about stretching the chassis to correct the wheelbase. This is done routinely. I know it would take work but if the chassis is sliced front to rear down the center, held in proper alignment (just like it is done when stretching lengthwise) and widened, not only would it solve the location of the tires it would give more room at the rear for engine and drivetrain.
I say this without ever seeing a MR2 chassis and the amount of work involved but EVERYTHING is work on these builds. I think the advantages would be worth it.
Maybe the next builder could investigate and lets us know the feasibility.
For now, I just throw out the concept.
lance345, you are doing a great job. Keep going.
RT