i havent used any spacers, new U12 discs are perfect width for caliper (but dont remember the measurement) can measure though

the surfs used the same s12+8 as well, cant be 100% sure what model mine are off, but i have gotten a few sets over time, always described as hi-lux calipers

i am running stock 1200 coupe master with no booster on rally car (that is using vanette drums on rear, which are larger than stock 1200 ones) brake bias is quite good

i am running stock 1200 coupe master on the raod car with bluebird disc over drums on rear, that has rear bias, so a brake bias valve installed on the rear line would be handy
engineer has recommended minimum 7/8 inch master for this setup, but i haven't fitted one yet, (this could mean an increased pedal force is required and therefore need a booster) but i have been running for years on stock 1200 master with no problems

to be clear..... for this all to fit.....:

caliper bolts straight to strut
disc needs precise redrilling to mount to hub
caliper needs grinding around outside to fit under 13" wheels
pads need grinding to clear the centre section of the disc

a brand new set of pads (cheap standard pads) on the front of the rally car lasted 3 rally seasons before being low enough to warrant replacement.... so they dont work very hard, and we have never had brake fade from them either, that includes stages that are 20-30kms long with the majority down steep hills, i think we have had the discs glowing red though