All the wheels with 5/10 lug on 7.25" bolt circle are hub centered.
You can enlarge the center bore in the older wheels to 5.25" to fit on the P30 hubs. Or use the 19.5" P30 wheels, or find 20" or 22.5" wheels from the mid 50's and later that already have 5.25" center hole.

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-