question about centers for old style mags

[Ozark Tim]

I think I went through this once before but am wondering if there is anyone who has any ideas on this subject.
I recently purchased a 72 3/4 ton truck that has old vintage aluminum slotted mags on it. Love em! I was given the original split rims and hub caps as well with the truck and also a set of conventional rims to boot. Alot of options!!! I want to run the slots on it but they have no center caps on them.
They look to measure 4.75" dia. openings.
All I have seen available are 5.1" dia caps.
I have machined wheels out before but that is quite a chore for me so would rather not if at all possible.
Thanks
Tim