i didn't want to wait, so i'm using mine as a base line...
alright. maths.
8.0" et34 w/ 225/40 tread is producing ~25mm clearance from the strut to the inner edge of the tire on full left-hand lock (LF wheel was used for measuring).
if i were to install your wheel, the inner edge would be 14mm closer to the strut.
and an additional 15mm for a 225 --> 255 tread (255-225=30... 30/2=15).
~25mm definite clearance compared to 29mm loss = ~4mm deflection of the tire on the strut. and this is assuming the sidewall cross-section doesn't change.
methinks a minimum of a 5mm spacer is required, maybe bigger. hell, at ~4mm, a 245 tread may still rub without a spacer.
dubbe, i think you're hosed. but i really want you to prove all this wrong... i would love to put some 255 tread up front!