Swap the seats for TT ones and save another 40Kg
You can get plenty of rear tyre under the D2. The rear diff is the limiting factor though, since its not designed to take the full load of whatever monster engine is up front. The RWD B5 guys often break them - first the support bracket breaks in half so they upgraded to billet. Next, they shredded the ring and pinion so cryo-treated those. After that either the casing splits in half, or the rear shafts snap.
Tbh I don't really understand RWD conversions in Audis. Just buy an E36 or E39 which are better cars than a hacked up Audi could ever be.