I put four new Coopers (245/60) on mine this spring. Very happy so far, but no long trips yet and no rain driving (not that there will be much). The other nice thing about the Coopers is they have a T speed rating vs. S for the BFG's. And they were about $100 cheaper than the BFG's when I priced them. Very surprised about the BFG's being discontinued. They were definitely available a few months ago. I agree that the Mastercrafts are an option, but I concur that they are probably the same as the Coopers. And I have not verified this, but it seems like I've seen street legal 15" Mickey Thompson's in Jegs or Summit catalogs recently.
Going back to the original question of "How Long Do Tires Last?": I generally agree with the 10 year rule, plus or minus (mine were 12 years old when I replaced), but interestingly, the shop I bought my new Coopers from also buys and sells used tires. He ended up buying my 12 year old BFG's! $20/tire - knocked off $80 off the price of the new tires. I was a little surprised and have pondered who his customer base is for 12 year old tires. The only thing I can think of is someone that wants to sell an old car and be able to claim "newer tires" - these only had about 6K miles on them.
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1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.