time to upgrade the Master Cylinder in preparation for my T100 caliper swap - the bigger pistons on the T100 calipers need a slightly bigger MC bore. The '90s T100 1 tons have a 1-1/16" MC bore vs the popular 1" bore found in many mid 90's 4runners and LandCruisers - bigger isn't necessarily better when it comes to the MC bore. A bigger bore moves more fluid, but produces less hydraulic pressure with the same amount of force on the pedal. In this case, I wanted to match what was available on the T100.
here's my $50 ebay master cylinder, brand new - note the 1-1/16" cast on the side

out with the old 7/8" bore MC

in with the new (and the aluminum looks much prettier than rust

)
it was a simple bolt on swap, no drama. The front brake line needed to be bent a bit to match up with the T100 MC port. I didn't bother to bench bleed it, prefering to do it on the vehicle with a rag under the lines. Initial driving impressions are good with pressure building and the pedal firm very near the top of it's travel, though when I get the T100 calipers on it should soften up a bit. I would not recommend this size MC with the stock 1st gen calipers as it could get tiring to drive with the extra firm pedal. On a 2nd gen with the "S12W" calipers though, it might be a nice upgrade that would give a better pedal feel.
I cannot personally vouch for this cross reference:
Brake Master Cylinder for the following 1 TON Models:
1994 Toyota T100 Pickup : 4-2694 2.7L DOHC
1994 Toyota T100 Pickup : V6-2958 3.0L SOHC
1995 Toyota T100 Pickup : 4-2694 2.7L DOHC - Notes: w/o ABS
1995 Toyota T100 Pickup : V6-3378 3.4L DOHC - Notes: w/o ABS
1996 Toyota T100 Pickup : 4-2694 2.7L DOHC - Notes: w/o ABS
1996 Toyota T100 Pickup : V6-3378 3.4L DOHC - Notes: w/o ABS
1997 Toyota T100 Pickup : 4-2694 2.7L DOHC - Notes: w/o ABS
1997 Toyota T100 Pickup : V6-3378 3.4L DOHC - Notes: w/o ABS
1998 Toyota T100 Pickup : 4-2694 2.7L DOHC - Notes: w/o ABS
1998 Toyota T100 Pickup : V6-3378 3.4L DOHC - Notes: w/o ABS