You can fit a 265/75/16 or 275/70/16 on stock 16x7 rims, not gonna lift ya very far though...
You didn't mention if you've got a 4x4 - if you do and you want a cheap lift, get some 2" or 3" front coil spacers and a rear AAL (add-a-leaf). They're plentiful on eBay or from a number of different lift manufacturers. The AAL will roughen the ride, however it is the cheapest way to go - not the best way, but it will do the job of lifting the truck.
BTW, If you decide against an AAL and want to use lift blocks - DON'T stack them! Remove the stock block, add the 3" inches of that block to any block you want to buy and get that size (i.e. if you want 3" total rear lift, get a new 6" block, remove the stock block and add the new one). Again, not the best way to get rear lift, but that can also be a cheap way to do what you want to do.
I would recommend saving up for a proper lift kit (new front and rear springs), but there are plenty of folks that go the route you're looking at currently.