My brother put 35's on his '80 about a month ago. I warned him not to, knowing that these beasts can't spare what little acceleration they have to begin with. But after running it for a while, it's not as bad as I thought it would be. Try to get a new set of wheels too, that way you can switch out to the 33's when you want to go racing again.
I went with the 35's but will take them off after my spring trip to Georgia. I highly recommend a second set of wheels, that way you can go back to 33's in 30 minutes if you're going to use it as a DD for a while. I wouldn't want to tow a trailer with 35's, though in fact, I wouldn't want to ever HAVE tow a trailer again with an 80.
I ran 35s and a 4" lift. I didn't really see a huge improvement off road as compared to stock 31s. Granted I don't wheel the hell out of my truck but I think I take it further than most "normal" people would. I switched back to 31s and took off the lift. I have had no regrets the past 10 years or so. When I buy new tires in the next month or so I will go 33s and stay stock height.
Flat landers are ok with 315s 35s on 4:10s.
My in town driving is 10 mpg. When driving 60 mph all day non stop got 345 miles on 23 gal. once.... that's 15mpg. My Lexi does ok.
