"Do they make a drain receptor with female threads on the inside that could be glued to the 2" pipe afer the base is set, and with the drain grate screwing into that?"
They do but I'm not too sure you can use it on a manufactured shower base. It's called a "flange type shower drain", (see image) and its used with custom built tile showers.
We don't build/assemble shower enclosures. A plumbers work ends when we do the drainage since the shower valve's already in place. You might try reposting your question over in " Internal Home Improvement" Good luck, Tom

Thanks for the help Tom. How do I go about reposting this question in a new category without retyping the whole mess.

Other than having a moderator move the thread, you can also just highlight the text, copy, and paste into a new thread started in the internal home improvement section.

Thanks for the help Tom. How do I go about reposting this question in a new category without retyping the whole mess.
I'll move it for you. Tom