Anders, I have been researching this for you. So far, I have talked with Bird Nest, Bob's Bird House, Concours Parts, Pat Wilson's, Dennis Carpenter, MAC's, Green Sales, Obsolete Parts, Tbird Products, Tbirds Southwest, Classic Cars Unlimited, partsetal and Rare Parts in California. So far, no luck. Several of them are doing some checking for me and will get back with me. However, Doug at Dennis Carpenter told me that his parts books shows that the rear Arm & Bushing Assembly for the rear upper control arm on a '58 Tbird is Part # B8S-5500-A. That part consists of a new control arm with the bushings on it. However, Don at Bird Nest told me that about the only way you are going to find that is as part of a bushing kit. He also told me that the bushings for the front cannot be used in the rear. They are different bushings in the rear.
I have been searching by that part number, but, so far, no one has it. Except that Rare Parts in California might... They have a Part #17846 which they call a rubber sleeve, which might be the rubber bushings. But the cost on that is $250.45 just for the bushings. Their Phone number is 209-948-6005 email firstname.lastname@example.org
Bird Nest has the whole replacement kit, but it is like $795!
I am going to look for that part number that Dave gave us, but I was told that the four rubber bushings for the rear are NOT the same as those on the front, and neither are the control arms. Aren't there four rubber bushings for the front control arms? Two per side. If so, then you would think that kit would say 8 instead of 4. But then again, if they are the same bushings, one would have to order two kits, I guess, one kit for the front and one for the back? However, as I said, I am told that the front bushings are different from the rear bushings...
Back to hunting...
I just talked with Kanter. They do not show the rear upper control arm bushings in their stock. However, they were closing, and she is going to do some more looking tomorrow, not only for the bushings, but to see if they happen to have the rear control arms with the bushings in place.... She will let me know.
Dave, do your books say anything about the REAR Suspension Upper Arm Inner Shaft? Could that be Group 3062 instead of 3068? There must be a Group for the rear suspension.
It only gets worse... I just talked with the Vintage T-Bird Sanctuary up in Oregon. They also have the bushings kit that does both sides, upper and lower. $841.29 for the kit. This, like Bird Nests, I think, is just the bushings, nothing else.