A buddy of mine has a full set of 245/75/16 BFG MT's. He said that I can have them if I give him the tires off my X (265/70/16). Is it worth it?

It depends what you want.

That tire is basically the same diamter, but narrower than your current tires.

What tires do you have now? If they are the stockers, and you're looking for an MT then I'd make the switch. (Also depending on the condition of the tires he's giving you)

Yeah, the tires I have on now are the stock long trails. The tires that he wants to give me have about 50 miles on them. He put the on his Rover and it broke down, instead of fixing it he bought a new FJ and lifted that. He just needs my tires to put back on the Rover so it can still roll.

OF COURSE it's worth it if they are good M/Ts. BF Goodrich Long Trails are crap.

Just remember your road manners will suffer a bit.