I would think it would depend on the type of driving you're going to be doing, but with 500+ HP, I guess we already know.
3/8 on the wheel lip, 1/4 on the spring side obviously means you've got that tire size maxed out, with eveything shortened/offset very well to end up with that result. Judgement call. Most have said that's not enough, so the safe route obviously would be to drop to the 255 width. That will give you another 7/16 roughly per side for a total of a little over 3/4.
Without rolling the fender inner flange lip or moving the springs inboard and reshortening the housing or new wheels, you don't have much choice. I can't imagine I'd do the options to gain a tire size additional clearance.
Are your stock springs the originals, or new replacements? that's going to make a big difference on how much body roll/lean you have.