You're going to pay north of $900 for an aftermarket case and I don't think anyone sells original cores online. You might be better off looking on Craigslist and see if you can find one for $100 or so. Coan sells complete glides for $900. They're easy to work on if you have a little mechanical ability. What's wrong with your case?
I've got a PG in my 65 that I'm going to be taking out. and probably sell. It's a 1.82, manual valve body, Hardened hub, pump modified, 6 pack hi gear, stock reverse. It's a footbrake trans I put together. Also has a deep pan and hardened input. And a shift lever for a Hurst Quarterstick. Wish you lived closer. Dave