since your truck is a 91 with IFS then any calipers made for a
truck from 86 to 95 will fit your truck. What you want are the V6 IFs calipers since they have bigger pistons and more power than 4cyl calipers. V6 calipers require more fluid so you probably will want to buy a brake master cylinder For a non-ABS FJ80 which has a bigger bore than your current BMC. you can order all these parts @ www.Marlincrawler.com but they are preety pricey, i would try to get them from your local parts store. Iam Currently in the middle of this swap on my 85 but it is a little more extensive on a straight axle, I have done alot of research about this swapp and as far as i can tell the FJ80 BMC bolts right up. I am not 100% posotive because i just picked these parts up from my girlfriends dads Shop on my way home from wrestling practice tonight. If you want more info i posted questions on this subject on this website last week about this. just type in "Fj80" or "Brake master cylinder."