My '73 came with an A&E awning with arms like you show in your picture. My roller tube was intact, but the awning material was long gone. I lucked-the-heck-out one day as I strollled into the local RV place and they had a bunch of awning roller tubes lying out on clearance. I picked one up in the exact length I needed for way-cheap. Anyway, it was manufactured by Carefree, so the little end-cap widgets that attach to the end of the arms did not match what I needed. I was able to drive out a single roll pin on the new ones and swap the end-cap widgets between the old and new rollers, and I was in business!
See the pic below for a comparison of the two. The chrome colored widget is the original, the white is from the new roller. Both rollers had the same sized axle.