You can find LT tires in other than 16" rim size but you have to look far and wide. One member posted the Hankook tire he found but I'd have to wonder about availability, especially if you got a flat that couldn't be repaired (not necessarily a blow out). The availability of that tire cuould leave you stranded for a while.
If you are going to change wheels you can find steel wheels pretty inexpensively. If you want to upgrade to aluminum wheels, that tends to up the ante. I did just that, I'm done with the ST tires so I did a little price shopping for aluminum wheels in a 16" rim size. I was trying to keep it at under $100.00/wheel and I hit what I think is the jackpot. At
Shadow Trailer Parts & Accessories AKA
TrailerandTruckParts.com I was able to purchase 5 aluminum wheels at $93.00 each after CA sales tax of 8%, that worked for me so I'm just passing on the info for anyone that may be interested.