Any shop with cup and cones should be able to balance it in a regular balancer. Iknow the newer snap was n machines and corgi ?? It’s a high end European tire machine have small diameter shaft and fit more wheels. what about a bubble balancer ?
You could remove and remove the bearings and scrub all of the grease off, reinstall using light oil on the bearings. That way you could determine how out of balance, where the heavy spot is, being at the bottom at rest. That is how we did them at a tire store in the 60's. Look at this link. https://e-quipfix.co.uk/wheel-balancing-101-static-vs-dynamic-wheel-balancing/
think i'll start out with the static method. should the spindle be level? i think it would have to be, wouldn't it?
Back in the 60's there was a balancer that spun up the wheels on the car. They incorporated some sort of a strobe light system to indicate where to put the weights and how much weight You might be able to find one in an old shop that has been around since the 60's or 70's. Good luck
I race and street drive mine. I have done drag week for several years. I have never balanced them and they go almost 200 mph. You might be trying to solve a problem that's not there.