I used 1/2 10 acme for all three axis on my machine with dual bearings at the motor end only. The other end has a bearing, but it just floats on the end. I didn't use AC bearings, just plain deep groove ball bearings. I have a bench top mini lathe and mini mill which made things a bit easier for making parts. You should be able to find a machine shop that can prep the acme end for you.
I took the acme and turned about 2" of the end down to match some 9 mm ID bore bearings with a small step near the threads for the face of the inner race. I then turned about 1" of the end down to 5/16" and threaded it for 5/16 24 nuts. And finally turned 1/2" of the end down to 1/4" to match the coupling to the steppers I used. The other end of the acme was just turned down to the 9 mm for the foating bearing. For bearing mounts I bored a hole through a 3/4" aluminum plate the size of the ID of the outer race of the bearings. Then bored the OD of the bearings in both sides of the plate for the bearings to slip fit into. The bearing mount could be made in three parts (layers) if you don't want to pay for machining work....
I've been using mine for almost 2 years now and the the bearings are still tight and smooth.