i thought it looked a bit familiar, couldnt put my finger on it, lol
yes, they are 24mm offset, and the fronts do stick out a bit (95 spindles). if i can get my motor fixed and afford a new set a wheels, theyre going to be either 17/18x8 with stock sn99 offset or x9's with a 30mm offset, even with the 245's and stock suspension i have rubbing problems (k-member too far forward, will be fixing if i can figure out the measurements i need).
if these are street wheels, why not just run a 255 all the way around? even with your suspension, i highly doubt you'd notice a huge difference just driving around on the street, plus it'll be easier to turn if you have a manual rack.
as far as 17's being scaled down, they are, but iirc actual saleen made a 17" version of these wheels too, or at least one of the sn wheels anyway. they still look a bit odd sometimes though, at least to me, especially when compared with an 18.