I want to buy a psa pa-9 lower with sba brace. They are glock style i believe, will they fit most upper assemblies? Ie foxtrot mike, joe bob's, etc? What upper should  i like for?

is there a particular reason that you don't just get a PSA 9mm upper at the same time?... I shot a PSA 16" blow back upper for about a year for USPSA PCC competition without a problems, it was coupled with a NFA billet lower, but my back up carbine has a PSA PA-X9 lower that was made for them by NFA, and a PSA 16" upper ( it does have the G9 hybrid bolt with the pistol style extractor)...I'm not sure of the manufacture of the particular model you quoted.... the PA-X9 doesn't get much use as the primary works fine...a friend has a PSA forged Glock style lower that gives excellent service... I would, however, recommend a 9mm bolt that uses an AR claw style extractor rather than a 1911 style pistol extractor...

Foxtrot mike makes one with a 3 lug adapter, and it seems pretty well made. I am just looking around. Didn't know if psa's lower ar9 compatible with other manufacturer. Thanks for the input.

Yeah, the lower will work with a standard upper.  You just need a bolt cut for glock mags.

When I got mine (carbine stocked complete lower for $150 w/ free shipping on a daily deal) they had no carbine length uppers or bolts in stock.

Used a Spinta bolt, NFA barrel, and Anderson sport/slick side upper to finish it out.  When I swapped the carbine stock for an A2 style I wanted to keep the known-working spring/buffer/bolt combo so I made a plug to shorten the interior of a rifle extension to be the same as a carbine extension.

I bought a PSA AR9 pistol for a PCC match and found out I couldn't use it (no braces allowed) so I found a cheap 16inch 9mm barrel and used an extra A2 upper I had lying around and with the lower and bolt from the pistol, used it to shoot the match.  350 rounds without a single problem.  Any upper should be good to go as long as you have the correct bolt and buffer set up.