235's on the front would have worked fine. I agree on the 285's on a 10" rim. Most MFG say 275 is the max which is the size I would have gone with. But your choices will work fine.

 

I was surprised to find that TIRE RACK does not carry ANY 275/30 tires.

 

You could have gone with a 275/35.

 

I'm running 245/40-18 on 18x8's and 275/35-18 on 18x10's and am loving it. I would think 285/30-18 would be fine on 10" wheels from looking at mine (maybe even 295/30-18). 265/35-18 on a 10" wheel IMO is too narrow a tire and causes the wheel lip to stick out further than the tire sidewall.

Dan
'91 928GT S/C