Hi Ziggy
I have a 91 GMC 4x4. I didn't want to spend alot on a liftkit. I purchased a front torsion bar level kit from Ebay for under $100. It allows you to adjust from 1 to 3 inches. I run 285/16 Goodyear MT/R on mine with no trouble.
The MT/R's are 33 inches tall and about 12 inches wide(10.5 tread). I use a 16x8 rim and I have no trouble. It takes about 3 to 5 hours to install.
And I have tested mine in some pretty rough trails and no troubles.
You might want to check wheel alignment after. I did and it only needs minor adjustment.
http://myworld.ebay.ca/springman98/