I have so far a stripped PA-10 lower and I'm looking at the Freedom upper. It does come with a a Mlok rail but what if I wanted say a DD rail? Will any rail for .308 uppers fit? I was told PSA uppers can not use other rails. Is this true and what maker has rail hand guards from it? I HATE Keymod and Mlok is tolerable but prefer good ole rails with my KAC panels. Having big hands, I like the girth.

DPMS Low .308 type fits.  I'm using a 15"  Midwest Industries M-lok MI-308SS15-DLM. Works Perfect.

I found this site to be very helpful.
PA-10 handguard