Greetings Terry Inman!
Welcome to the Forums and the world of Vintage Airstreams!
Originally Posted by TERRY INMAN
I have split rims with L78 15 LT They are old and the split rims must go. Any ideas for new tires and rims?
My suggestion would be to tow the rig to a nearby tire shop with whom you are familiar and ask that they measure all clearances to verify the best tire size to order. With the Vintage single axle Airstreams, tire clearances can be quite tight, and getting the proper fit can be a bit of a challenge. The advantage of having the tire dealer take care of these measurements is that if a mistake is made and the new tire/whee combination doesn't fit it will be the responsibility of his employees rather than yours -- this saved me the cost of a set of aluminum wheels that the tire shop ordered with an incorrect off-set a few years ago.
The tire dealer will also be able to measure your existing wheels for off-set, center hole, etc. to help you select replacement wheels -- my Good Year dealer was able to do this for my '64 Overlander, and the steel trailer wheels he ordered fit the trailer beautifully (he didn't stock Marathons or trailer wheels, but was able to order them with 48-hour delivery).
An alternative if you are not comfortable with towing the coach to the dealer would be to take one of the current tire/rim combinations to the tire dealer and ask that he measure both and suggest the best ST tire and trailer rim to substitute for the current combination -- you will want at least 2,600 pound capacity on the trailer rim.
Good luck with your wheel/tire selection!