Dogboy....I believe the calipers in question are 40mm (does it really matter--they're bigger!) and they are of the four piston variety. Don't try to rebuild them, as toyota wants to do it themselves (for quality control...can't argue with that) so they charge a ton of money for the pistons and seals and a reasonable amount for rebuilt calipers.
Look for anything with the 1" stamp on the side (T100 {4x4 or 1 ton only}, 4Runner, even a Supra). Just go to the junk yard and pay $10 bucks or so. You'll have to bend one line a little....just go slow. Otherwise it bolts right up. However, I could not get the brake light to work with the new wires (gave up). The light still works, but not as a warning light for when I'm low on fluid (i.e. the parking brake still lights it up.) I just taped it up.
I did this about two months ago and it really helps! Plus the addition of SS brake lines and DBA rotors (all from MAF). If you have any more Q's post up.
Here's some pics:
Where I shaved the dust cover (top and bottom)...
The trimmed wear bar on the caliper (no worky with it)...
You must grind...
The finished product...
Cheers,
Matt