Vented rotor swap
Solid toyota front axles come with solid (unvented) rotors
By buying rotors from '81 and up Toyota LC FJ40 and fj80
and calipers from an IFS Toyota (86+ P-up or 4Runner).
You can swap to vented rotors. Does not add any width to the axle.
Rear Disc brakes
Rear disc's are pretty straight forward on toyota rear axles.
These guys sell caliper brackets that bolt on
or you can build your own
Many ppl have done them diffrently using different parts, but most us chevy 1/2 ton front rotors and calipers from chevy S10 or if you want an ebrake Cadillac Eldorado.
Tons of info here: