Visit a truck tire dealer, let them look at what you have and tell what you need to order......and maybe sell you one too.
The front rims and the back ones might not be the same.
Because of that, I carry a spare "tire" only without a rim.
If you do that, you need to specify that the truck they dispatch needs to be capable of putting your spare on the rim at the side of the road......OR be able to tow the entire rig to a place that can.
'07 Damon Outlaw 3611
CanAm Spyder in the "trunk"