Now now...be nice

My car runs on 12's due to the metro vented (12X6 from Hillman Imp Sport) and I was thinking of ways of rustling up a spare set to run autocross etc on without killing my road tyres.
I'm eyeing up the idea of having a set of 12" GT rims widened...otherwise there's bugger all else available in 12" without spending big money.
If I put 4.5" rims on with the flares I have it'll have that Escort rally look.....s'pose it's not the end of the world....
are morris 1300 wheels the same stud? they go under with no flares but may be to far backset? inset? whatever its called when they 'stick' inwards, ive got a few i could send ya down