Re: 35\"s on my 90 K5
Go with any 6" system. Systems are usually the term for lifts that include rear springs and not add-a-leafs and/or blocks in the rear. I have a 6" all spring lift from Tuff Country, and Im running 35x16 boggers. Tuff Country came highly recommended to me, and I absolutely love it. The harware is high quality, I get tons of flex (I even make my buddy's all coil suspension on his Cherokee look stiff.), and the ride is superb. The four 6" springs, all the neccessary hardware, and a 4" raised steering arm cost only about $750. I rubbed a little in the front when Im flexing a lot, but that's only because I'm running a 16 inch wide tire. (Besides that, they're Boggers for God sake.) I fixed that little problem with a little trimming. However, your mud terrains are most likely 12.50 inches wide, not quite as tall as the boggers, (taking the bogger tread into consideration) so you should be able to pack those tires into uncut, unmodified fenders quite nicely. If you can, avoid a body lift at all costs... you get more frame flex, you get tranny shifter issues, the radiator is raised above the fan, and your bumpers look like [censored]. Go all suspension if you can. Hope I could be of assistance.
Chris