The boot will fit mate the only difference with them is at the bottom of the 3.5 they have'nt got the reses in line with the bottom of the rear clusters.

If you can fit a mk4/5 rear lid to a mk3 a 3.5 will go on no probs and as for the mirrors you just need to cut a bit of metal away to fit 3.5 mirrors but they look the nuts when on.