I do not think it was common for theses bolt patterns to change over to alcoa's. I have only seen 2 sets of alcoa's in 6 bolt pattern. One on a truck on the internet and the set on my truck. Alcoa stopped making them in the 1984. I have never seen a 10 bolt GM pattern alcoa wheel.

Shane
1959 Apache 3100 Fleetside
1959 Apache 3200 NAPCO
1957 Chevy 5700 Low Cab Forward
1959 GMC F370 LCF
Another 1959 Apache 3100 Fleetside
1959 Chevy 5700 LCF
1946 Chevy 1/2 ton
1958 GMC 600
1974 Elcamino SS