Drum to disc conversion

The common setup is to use the Hilux knuckle housings with the matching disc brake rotors, calipers and spindles. I would think using the Hilux master cylinder too for this application.

No idea of cost but a few calls to some wreckers to get an average price. At a guess you could probably buy the whole front axle housing for $300 - including the diff and axles and just strip off what's needed.

I didnt do the conversion, but my 1984 FJ45 had factory front discs. I imagine you could pick up the swivel hubs and calipers for pretty cheap from a wrecker- the last of the 45series came from factory with front discs and power steering.

It set me back just over $200 trade to get all new pistons (they are 4-pot callipers), boots, pads and discs from Don Kyatt (welshpool, Perth) about 3 years ago. I reckon if you do it, get new everything and give the callipers a good flush of the fluid galleries.
I dont know for certain, but you may need to get a new master cylinder too- The early 45 series had a single outlet on the bottom of the fluid resivoir, but the later models had two openings that fed the cylinder. That said, I did successfully run with an old master cylinder, but I could never completely stop all the fluid leaks.

I fitted discs to the front of an 81 FJ45 in late 82, used stubs, hubs, discs etc from a hilux. Also had to change the master cylinder to (from memory) to a 60 series m/cyl which has a smaller bore. I guess a master cylinder from a later 40 series with disc/drum would also work.
You may also have probs if the rear wheels have two wheel cylinders (most drum/drum vehicles) or just one (later drum/drum and disc /drum) as the smaller bore master cylinder may not push enough fluid to work the back brakes fully.
Also watch the proportioning front to rear as the early drum/drum vehicles used a proportioning valve which was mounted beside the master cylinder, later vehicles used the load sensing one on the rear diff/chassis.

Nige
Especially if you own a real early 40 with no full floating rear end...
Best to look for a complete disc front diff from a 40, 70 series pre 1990...and bolt straight in...all these diffs run a 4.11 ratio unless they have been changed to aftermarket....Use a 60 series master and booster or the disc front 4# series.
Andrew