I feel Ya there brother, never a happy day undoing something You just did. And yes, You are correct, You'd need to swap knuckle/spindles to hop up to 10". That one should be easyI'm not opposed to the 10" drums, I just hate the fact I already did everything and now am screwed. Don't you need to source a new spindle for the 10"?
w/so many swapping late model knuckles/arms/brakes onto the older A's like Yours. If I had a set I'd send 'em to Ya for the cost of shippin' 'em, but both My GT's came w/the 9".
I did want to switch to LBP 'cause I do drive crazy, so I've got 11.75" disc's up front & 10"x2.5" drums(for now) out back.
The way I see it You've got three upgrades available;
1) Find the OE 10" drums & related, they will stop very well for any normal driving.
2) Find the OE K-H front disc set-up & related, extra very well stopping & insurance for any extreme circumstance.
3) Get the Scarebird setup & related(which also requires the 10" knuckles), same as above w/easier to find componentry(for now #rotors).