Any reason you can't chuck them in a 4 jaw and bore them in the lathe?
If I only had a couple to do that's what I'd do, no need to make fixtures unless you want to or expect to do lots of them.

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-