35's ?

[HummerJim]

If you do any serious water or creeks, a lift can help, but don't forget to raise the exhaust tip as much as possible and check your trans and axle vent tubes for extensions.
I had a 1986 Ford F250 4X4 Heavy Duty with a 460 engine that I had lifted 6 inches. The work was done professionaly by Midwest 4 wheel drive - home of Big Foot. I can definitley tell you the negatives.
No matter how good the work, they will eat up universals on drive shafts on a regular basis.
Don't lift it without a driveshaft loop.
Raising the center of gravity makes it much tippier, and in a serious crosswind on the highway the front end will hunt and search a lot.
Understeer in the dirt, snow and mud will be worse than stock.
Get a larger transmission cooler, because it will run hotter do to increased torque on the driveline because of the driveshaft angle.
You may need someone to fabricate a custom emergency brake steel line, because a stock one normally doesn't have enough play.
It was fun and I liked it, but unless I did more serious offroading and water, I'd think twice. Living with it day to day was another thing and now the state of Missouri has set maximum bumper heights that might make getting an inspection for plates impossible.