I had an '87 Hardtop MR2 I was going to turn into a track car. It had no power options so would have been the lightest stiffest MKI MR2 from the factory. I ended up abandoning that project when I got my MKII MR2 Turbo. The MKI has pretty bad brakes to begin with (relatively speaking), suspension options were harder to find than the MKII, smaller stock rim/tire size, etc. etc. etc. Plus the engine bay way pretty small. The MKII was way easier to work on.
Now the '77 Celica I've got certainly doesn't have great brakes, but there are many swaps I can do from late 80's toyotas that will be bolt on or nearly so, and the car's lighter and the engine bay bigger.
I really loved driving MR2s (owned 4 in total) but I think I'm sick of the Japanese Ferrari now!
So many options for the Celica, the only thing stopping me from putting in a 2JZ-GE (and then using a turbo kit or the factory GTE turbo stuffs) w/W58 is the weight. It would practically drop right into the engine bay. Some guys use engine mounts from the MKII supra to put 7M-GTEs into late 70's celicas. It's all doable...