I'm not really a fan of the Duratracs. Nothing specific, I just haven't heard folks say good things about them - but man alive, ask 'bout the KM2's! Whoo wee!
As for sizes, here's a basic rundown of what's available to me in a 16" rim, and the number of tires for that size:
315/75R16 = 34.6x12.4R16 (27)
325/80R16 = 36.5x12.8R16 (1)
345/75R16 = 36.4x13.6R16 (1)
35X10.5R16 (2)
35X12.5R16 (6)
35X14.5R16 (2)
35X16R16 (1)
36X12.5R16 (2)
36X13.5R16 (1)
36X13R16 (1)
36X14.5R16 (2)
375/65R16 = 35.2x14.8R16 (1)
37X12.5R16 (4)
37X13.5R16 (1)
37X13R16 (1)
37X14R16 (1)
Note *most* of all of those outside of the 315 are Interco (Super Swamper). And from what I was told today, they went bankrupt and got bought out - almost didn't make it, and suppliers are scarce for them right now.
Steve, I 100% agree with you on the size issue. Check out the 17's selection compared to 16's:
355/70R17 (36.6x14R17) (1)
36X12.5R17 (1)
36X13.5R17 (1)
37X12.5R17 (13)
37X13.5R17 (3)
37X13R17 (1)
37X14R17 (1)
38X13.5R17 (2)
38X14.5R17 (2)
38X15.5R17 (3)
And just for giggles, here's your 15's:
36X12.5R15 (3)
36X13.5R15 (1)
36X14.5R15 (2)
37X12.5R15 (3)
37X13.5R15 (1)
37X13R15 (1)
37X14.5R15 (1)
37X14R15 (1)
38X12.5R15 (2)
38X15.5R15 (3)
And to your other point Steve, the only tires I see in your 37x12.50x15 are Super Swamper brands too.
The other thing that worries me is not only extinction, but just plain availability... if I shred a tire, I've got a spare. But how long it going to take to get that tire replaced? 6 months?