Good morning everyone
So lately I have been picking up vintage Keystone Kustom Mags whenever I have been finding them. I know I can get the blanks for the barrel.

Has anyone done this here? Looking for tips and tricks.

i have done the re-hoop process quite a few times, to different styles of wheels using steel hoops and aluminum centers, as well as making different offset or width steel wheels.
it's quite labor intensive, and requires superb welding skills, a large enough lathe to be able to machine a hoop or center to the correct press fit id/od, a way to straighten and true the wheel, plus exact measuring instruments/machinist tools.
i'm not sure what you are trying to do with the wheels shown, but if you are truing to restore them, in my humble opinion, you would be way ahead to find pristine examples and pony up the price for them.
chroming these days is not cheap, nor is restoring those aluminum centers.
i will go out on a limb here by saying you would have twice, at a minimum, the money into those wheels restoring them instead of buying reproductions or excellent condition originals.
so with that said, blasting, straightening [if possible], then painting or powder coating what you have, may be an alternative ? providing the centers are not cracked.
just my opinion and life experience with wheels of all kinds.
your mileage will vary.

A buddy loves Motor Wheel Spyders and has had several sets rehooped by someone who I believe is in Iowa.

I can see if I can get info on who it is from him.

Lately I have done several 14" to 15 " conversions to Magnums and also making the 1970 -71 "450" wheel.

On the chopping block next is AMC AMX wheels.

Getting the wheels to run true is the most time consuming part. Some wheels it takes no time others lots of time.

I use indicators on my lathe to get them the best they can be.

Hit me up if you have any questions about how to do it.

I've done a few steel 14" to 15 x 10. I don't have a lathe or any really special tools, but did use a dial indicator and got them very straight by mounting the centers up to an 8-3/4 rear end. We had no trouble getting the wheels balanced when we were done.

the picture you posted shows the way i do wheels.
before i used a lathe, i had a front spindle and hub from a dodge something or other, bolted the wheel to it, and used a solidly mounted pointer to lightly touch the wheel in the horizontal and vertical planes, then use feeler gauges to get the runout as close to .010-.025 as possible.