Again, congrats on your new acquisition. I hope some of what I had written is of help.
And again I'll relate that the task-ordeal of properly setting up the SAMA can be testy, and involved.
Even if all that you had was with all original feet, same with the SAMA, there's no assurance-promise that the SAMA is going to sit properly in both horizontal and vertical planes.
As an example, when I changed over to the SAMA, I found that I did have to relieve the left rear wood base corner brace where the SAMA sits. I could not achieve ample Belt Tension, nor did I like where the Motor Shaft and Pulley sat in relation to being properly centered in the Plinth Hole. Insufficient clearance in that corner.
I trimmed-shaved that area out easily, clean cut like it was done with a laser, I'm fussy about doing such right, and not a butcher job. I was then able to position the SAMA where all looked right, and insured that the SAMA absolutely does not touch any part of the Table. This is paramount.
At first I resorted to a simple piece of 4" Square Ceramic Tile to raise the SAMA to the correct, needed height.
But as I mentioned previously about my SAMA, it was not staying put and planted squared in place for long. Was no good. The Tile wasn't slipping, just the Feet were inadequate it seemed. Hence, and with exhaustive measuring, checking Herbie's specs, the change to the Herbies Tenderfeet underneath cured that issue. In my specific application, I got lucky and nothing else was needed, the precise correct height was achieved with the Tenderfeet alone, no other spacers or such needed.
I in fact have a pair of them MNPCtech Feet for the HW-19 brand new, never out of the box, but I doubt I'll ever use them. Thought later maybe I could've used them on some other Table, or give them to a friend of mine, maybe he could pop them onto one of his Vintage Tables?
If I change feet on my Table to those, then there I go all over again pulling my hair out trying to correct any height changes made with the Table, which will have influence-effect on the SAMA Motor's positioning.
It's a great Table, I like the modularity. Takes a little time to fully understand it, not that hard.
As for drive belts, and ones that I like, I've had good luck with the Black Tranquility Belts, from LP Gear, they are Nitrile, whereas I believe the original clear belts were Silicone.
Here's what those MNPCTech Feet look like on a HW-19. Being that the Audiopoints Feet might very well be MIA-NIS, these feet might be about the best bang for the buck out there, and are simple screw in affairs with the correct screw size, they're mounted up in 2 minutes flat. The Sorbothane cushioning should be better than the stock rubber was as well. In full MK-IV form, the HW-19 is not light.
IMO, the stock rubber feet were garbage. Harry's price, probably 45 cents apiece at most.
https://www.mnpctech.com/collections/turntable-lsolation-feet