I can't help with the bearings and rails, but there are several listings for 12-24 taps on eBay. They aren't as cheap as they were pre-pandemic, but there are still some reasonable prices at less than $4.00 per unit. There are currently 454 listings, but many are cheap offshore or lower quality US and European brands. I would stick with the HSS professional brands like Morse, Guhring, Greenfield, Nachi, Emuge, and others.
Here are a couple of the listings:
<p>LOT of 4- Morse cutting tools 12-24 spirial point steam oxide tap. EDP 34147. Unopened. </p>
www.ebay.com
CHAMFER: PLUG.
www.ebay.com
I have bought quite a few taps from ztsupply over the years. They've always had good products and reasonable prices.
I noticed the saw in the picture is similar to my 14" Delta 33-400. Yours has some additional bracing near the bottom of the legs. I'm assuming it's for greater stability when moving the machine from one location to another. I'm considering something similar as well as adding plates to the bottom of the legs for casters. I recently purchased a set like these for another machine and am considering them for the Delta saw.
Can you post a couple more pictures with more detail of the lower end?