Tire Sizes For 04 Silverado

My tires are practically bald now, and i'm shopping around for some good tires, but the selections are endless!! My 04 Silverado is a 2WD 5.3L (T) Engine, and I don't tow anything with it, and if I did, it wouldn't be big, or far. Anyways, the tires on it now are 265/70R16s. I want something smaller, perhaps 245/70R16s, 245/75R16s, or 235/75/R16s. The thing is, I don't know how much smaller I can go on the tires. Hell, if possible I would put on some 215s. Does anybody know the sizes that will fit my truck? I'm talking width wide (200,210,215,220,225,230,235,240, etc..) tread wise, I don't mind, since I'm hoping for 65, 70, or 75. They are 16 Stock Rims, so they have to be 16 inch tires. Any help...GREATLY APPRECIATED!!:banghead: :banghead:

I dont know the answer to your question but I'm curious as to why you want to go smaller?