The 1996 SC400 factory "blade" wheels with that tire size are a very good looking 16-inch rim on these cars. Best in painted gray but they also came in factory chrome versions. Note that you can't use any upgraded four-piston brake calipers with 16-inch wheels. SC400 factory brake calipers are the largest that can be fitted in this size.
I picked up the 6 spoke 95 SC300 wheels...... Better than the chrome turbine blade 15's.
Not a fan of chrome wheels, but the chrome is in great shape and at $100.00 for the set of 4. could not pass it up.
Do you plan to paint the center caps chrome colored? That looks pretty weird like that. I imagine they'd actually look better without the caps than with the mismatched colors.
An indirect answer to the original question: MKIV Supra NA wheels are 16", as opposed to the TT wheels which are 17". The NA wheels go pretty cheap, since everyone wants the TT ones for bigger caliper clearance. One of my cars actually came with a NA wheel as the spare, which tells you how high of demand they're in.