I have a 1968 with a straight 6 and monojet also.
For several years now, I have had a "saved search" on eBay for carburetors....here's a link
https://www.ebay.com/sch/i.html?_nkw...2%29&_svsrch=1
I have bought many, most in the sub $50 range. I've never got anything much better than extra parts. I haven't tried to run many of them. Even one that was a NOS Reman didn't run better than the one that come on my truck, that the guy I bought it from had just rebuilt.
I'd try to pickup the cheapest you can just to replace the broken part of yours. Get a rebuild kit and just use what you need to get it going and try to improve from there. Or, if you have time try out the full rebuild. They're a very simple carb.
I'm not sure what the deal is with the "Autoline Carburetor C9044" Rockauto has it listed and Autozone has it listed as a reman for the 1968. Over the years, it goes in and out of stock. I've often been tempted buy buy one and see how they run, but I've gotten pretty good at keeping what I have going.