I have ST185 Jap calipers (ie twin piston) now fitted to my car.
When I was searching for alternate calipers, I think the ST165 & ST185 were the same, but the discs & calipers were different from the FWD models (ie bigger).
The ST165 & ST185 calipers & discs will bolt straight onto your hubs with no mods, so just search for these from an importer.
I picked up my calipers for $100 for the pair (I already had the big discs so didn't change them) + $85 for pads.
If you get the twin piston calipers, make sure you get the shims & the old pads.
The pads you'll need as a sample when you get new ones (but not from Toyota, they only have the Aussie single piston ones listed)