Oh crap, This car is becoming a real project. Gotta go find my spring compressor and nos springs. In one of 3 places in 3 separate locations. I'm not sure if locating the bits is worse than putting them in, but I guess I'll find out.

I just learnt something about 10" steelies.

Change the rear wheel cylinders to 5/8" for sure. The 3/4" will seem to work fine until the first time you do a panic stop in the rain or on gravel or in a turn!

Agree with Alex re. wheels. I learned initially that NO 3.5" standard Mini wheels will fit S brakes. But then I was working with earlier cars only. I remember a "discussion" I had with someone saying they ALWAYS fit -- someone who had never used a 60s wheel. We were both wrong.

I went through all my old 3.5s a year or so ago -- maybe 30 wheels and most of them early ones. I recall only about 10 fitting on the S brakes I was using.

No it isn't. 
Not all 10" steelies are the sape shape internally.

I had to put 12" on the front of my spare Hornet as my spare 10"s didn't turn.

I did the conversion, and I like it. But I went whole hog and changed to Blue springs at the same time. Like was stated before you wil need rotors, calipers, drive flanges, and brake pads. The whole process took about six hours (not counting alignment) but I had to remove the lower arms because the threads on the rubber cones were rusted too bad.

It has been discussed many times that the rears do not do much when braking but it seemed to me that the pedal felt better when I later switched to 5/8th rear cyl from 3/4th.

Its a myth that 10" stock steel wheels won't fit over S disks.

I'd suggest you go ahead and replace the springs. I do that to most cars I work on. Huge improvement in ride. I have a 12 inch mini riding on 165 with 5 inch rims and old springs and it's the roughest riding one I have been in. My personal car has new springs and is on 145 x 12s on 4.5 rims and rides great. I also want to return to 10s but have bought so many 12 inch wheel and tire sets I need to use them up. My car is transportation first and a hobby second.

 I have run into disc that had a clearance problem over newer hubs. It has only happened with disc of unknown orgin. Brembos and the better quality disc have no problem. The two times I ran into this problem I chucked the disc in a lathe and took a couple of passes though and they were fine. Another option would be to use 8.4 drive flange and turn the disc down.

Steve (CTR)

good points Mur and Dave.

I've never experienced it, but recall Calver saying that many of the 7.5 discs aren't sufficiently machined for the later 8.4" hubs which were slightly larger on the outer 'nose' of the spindle than the older generation hubs....

Just something to watch for...

If this is based on parts from the 1990s, just change the rubber cones.

They're 12's and the same OD as 10"s.

12 inch rim works as a spare with 13's no difference than a US temp spare as long as you just run it a few miles. It probably still has the stock rack and pinion with the better ratio than the s/p. If the wheels are 13's the fenders are cut how are you going to fix that with 10 inch flares ?

Mur, the ride is bouncy and I'm sure the rubber springs are shot, but want to see how much of it is also in the tires. I've got about 8 sets of mounted 10's from minilites, to JAP, to cooper s, to dunlops, etc. All with good rubber. I'd like to try them before I start putting new rubber springs into the car. Just basically shaking it down as I bought it as an unfinished project.

One thing that impressed me was there was no tire rub at full lock. What doesn't impress me is that there's no room for a spare this size, and it means putting a rear on the front if I get a flat. Using a 10" spare from the boot, would not clear the brakes.

I like that the car has twelve or thirteen inch rims.  Because if it does not have ten inch rims, who cares what they are!

Thanks, hoses are new, but car has 12's or 13" minilite style with wide tires. I'm gonna go back to 10"s. Wheels/tires and brakes will be up for offers. Not gonna give em away. Wheels and Tires are new or near new.

I think most 8.4s runa 3/4 rear wheel cyl. 7.5s seem to balance better with the 5/8 rear cyl. Systems open might as well get it behind you. Hoses back there not a bad idea.

Steve (CTR)

And if you are loosening the flex lines and they are old you may as well replace them while you are at it or even upgrade to stainless.

Like has been said - Calipers, Discs, Drive flanges and pads.  You will almost certainly need to loosen the inner end of the flexi brake line and turn it to remove twist as the new calipers seldom line up with the old ones.

Takes about 45mins per side.

Rotors, calipers, drive flanges, and brake pads. 

I think that's it.  Outer CV is the same....dust shields ( if used ) would be different

lol...oh yea...forgot, brake pads