I've never seen the medium sized GM 10 lug Alcoa wheels, I'd assume they never made them.
They did however make aluminum 19.5" 10 lug on 7.25" wheels, quite hard to find now though I have found some (not for me).
The 6 Lug Budd alcoa's are alos hard to find, last set I've seen were on a motor home/RV. Which is a good place to look for the small 10 lug 19.5" as well.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-