ok thanks sounds like the way to go. would this be the right spec? http://www.ebay.com.au/itm/Brake-Master-Cylinder-Toyota-HiLux-4-Runner-LN86-LN130-/260696132371?pt=AU_Car_Parts_Accessories&hash=item3cb2b34b13

Nope that is the old cast iron one, I never found the right one on eBay, but I do have the make and models of all the cars that came out the 1" master.
 
I will post the pics up today also showing the install for future referance.

Toyota 4 bolt M/C's can be easily swapped between the models but you should replace an ABS with an ABS model, or vice versa for non-ABS.
Be aware that ABS and non-ABS M/C's have different pipe outlets, and they appear to also have different push rod depths.
(see pics of the 15/16" SW20 M/C)
 
BTW apart from the 4 Runner, Land Cruiser and Supra also used one inch bore M/C's
 
When Toyota changed to the larger brakes late '91 they also changed the booster.
Then they changed the booster again after 11/'93 with a more powerful one.

ok thanks for the heads up

I have a 4 Runner master with 4 pot calipers. I don't think changing the booster would make a different with either pedal feel or braking performance.

Depends if the car already has the later model booster though. If it doesnt there is a big difference.

After I upgraded to the I brought the larger booster, the 89 model booster is crap.

If your going non power assist, dont bother with any OEM units. You need a pedal which is a dedicated unit specific for non power assist. You will not have the right ratio with a power assisted pedal. You need this: http://www.ebay.com.au/itm/WILWOOD-FORWARD-SWING-MOUNT-BRAKE-CLUTCH-PEDAL-ASSEMBLY-TRIPLE-M-C-WB-340-3950-/140845643925?pt=AU_Car_Parts_Accessories&hash=item20cb0df895
and one of these: http://www.ebay.com.au/itm/BALANCE-BAR-ASSEMBLY-ADJUSTABLE-BRAKE-BIAS-PEDAL-BOXES-/220965872897?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item337297a501
These are also available at www.carshopinc.com . They also sell the master cylinders to suit the pedal assembly. The one I added from ebay is a forward mounted master cylinder which will suit best. Master cylinders cost about $80 each. You will require a formula to workout the ballpark figure for the master cylinders. You need one for the front and one for the rear with the balance bar to set the bias to your liking. You can also run a in car bias adjuster to make like easier too. $100
With this system you wont need many mods to fit it and it wont foul with anything under the bonnet but will need to have some lines or adapter to tap the lines from the OEM lines on the firewall to the new master cylinders.
If you dont like the feel of the brake, just buy a new master cylinder and install. They have a huge range so if you go to a bigger brake system you can upgrade very simply and easily.
Here is a thought on a cheap option for a sick caliper: http://www.ebay.com.au/itm/AP-RACING-4-PISTON-REAR-BRAKE-CALIPERS-PN-CP5410-4SOL-5SOL-W-LINES-NASCAR-/180916963034?pt=Race_Car_Parts&hash=item2a1f7dc6da
Only way to fly..
 

Here is a handy link
http://www.markwilliams.com/braketech.aspx

My 91T has standard brakes (+ ABS) and the MC needs new seals. The pedal slowly goes towards the floor. When I eventually found the right part number for the repair kit, it is "Discontinued". So going to replace the MC with a bigger bore. I was thinking 15/16" might be all that's needed to get an improved 'pedal', but this thread talks about going to 1".  I still have the original callipers and I see people here discussing going to the GEN3(4?) bigger brakes, which I am not doing at this time.
  So should I go 15/16" or 1 " ?    (and will the 4Runner version suit my ABS system ?)
 I presume I should also replace the booster unit...so any recommendation to go with the new MC ?
 Thanks chaps.