I've just changed from 235/85's to 265/75's. Both roughly the same height (around 32"). The 265 is probably a little wider than a D1 was designed for, however so far I am happy.
IMO anything bigger than 32"s on 24 spline axles is just waiting for a bang. I busted the front axle on my RR back when i had 255/85's (33"s) but from memory it was 10 spline back then.
It really comes down to whether you want to upgrade axles and change gearing as well.
