Yeah I run the 30X9.5 for winter due to I have a set of chains for it. and run 31X10.5 in the summer. You see the 30's on it now..Hunting season coming soon. Plus this is snow country and Big wide tires are the worse to have in the snow. Ok for mud but not in the snow. there is an extra leaf spring in the suspension. That gave it a little lift about 2" or so.
KAM
They make a 33 x 9.50 size
The problem with most folks is that they don't air down their tires to around 20 psi. I'd still put that brace on regardless, it is a MAJOR flaw with the Suby's, Chevy/GMC pickups from around 68-91 IIRC. What you need to look for are frame cracks right by the Steering Box.
This is the one a few of my buddies use on their Tow Rigs and they only recommend this one:
http://www.offroaddesign.com/catalog/steeringkit.htm. One of my buddies had to replace his brace, with that one. This one is built, the others are flimsy.
Your frame is more than likely cracked, as street driving can induce it. I'm just trying to keep you from......you know, because that would suck.
PS - You should know I enjoy your mild resto of it.
Going with the 94 350 was a good choice. F/R LSD's will be a nice feature.