As said 4i is drum on rear, but I have brackets to convert if you like to disc on rear, there are two types of rear caliper for discs either for vented ones or non vented ones, both take 273mm discs, 2wd cossie has 273 solid whereas 4x4 cossie are vented.
xr4x4 rear discs are 256mm, 4i drums are 228mm, but a LOT wider than std drums.
2.8 engine is crap, restricted ultimately by the siamese exhaust ports.
I had one rebuilt the engine, with modded cam, and modded heads, with DRY FUEL INSERTS, it was still slow, my previous 2.1 pinto AUTOMATIC was way way faster, and better on the rolling road as well.
It depends on how far you want to go, if I had to choose again it is a no brainer I would take out the v6 ans shove a tuned pinto in there.
Or failing that a 4litre V8 TVR crossbolt like I did!!, to my dads car for him, 240lbft at 1800rpm, but 190lbft at 1000rpm!!
I had mine on LPG, MUCH MUCH quicker, than a std one and went much better on lpg than it did on petrol as well
tabetha