[Flyin' Hawaiian]

Yes and no...

Spacers can be as strong as not running them at all, but it all depends on the actual thickness of them, as well as just how strong the lug bolts are, and even how much is threaded into the nut! As a general rule of thumb, you want 1½ times the thickness of the bolt threaded into the nut~ ie., if it were a 10mm bolt, you'd want 15mm of it threaded into the lug nut.
I'd say that it's just better to stick with a rim that is designed for our vehicles to be safe, especially if it's being used on the track! Why take the risk, as well as the added problems of tire balancing and added unsprung rotational mass!
Just me thinkin' out loud again!

 

[Flyin' Hawaiian]

Hey Malloy, come on over to Potholifornia and I'll show ya some really cool ones!!!
And Malloy's right on the old timers searching for rims, I too did the same thing a few months ago! Decided to go with the Compomotives for price and looks. I even tried my friend who works in a wheel shop and he said there's not many rims with a 0~+3mm offset in 16 or 17" sizes.
Now, don't let this discourage you in finding rims! The more folks searching, the more we'll be able to find that'll work for the Supra! I hope ya find a new brand that will, and if ya do, make sure you let us know what it is!
Good luck!!!