Tire rim for spare advice on 66

[msg]

Ive bought the tire bracket for the spare that suspends under the truck and was going to have it sandblasted and painted. But I dont have a spare for it yet. The rims are rally 15 x 8 w 6 lugs and Ive got front disc brakes. The long bolts that hold the tire to the bracket are about 9 inches from the base of the bolt head to the end of the threads. For the spare what should I hunt for? The same or would I need something more narrow width to fit under the truck bed?

Heres a pic of the rims i have