My buddy just acquired a RRA LAR-8 in a swap for a long over due debt. Seems like a decent .308 but the RRA stock sucks! Can he just swap out with any other after market stock? More than likely will be a Magpul. Seems like the hand guards are fairly proprietary but one would think a stock should be interchangeable.... any info is helpful!

If it has a collapsible stock on it, then yes...

Just double check to see if it's Mil or Com tube to be safe. Mil is straight and Com is slanted.

I put a CAA stock on my LAR-8 (don't laugh, it works for me) and was able to jimmy a Magpul handguard onto it as well. It was a tight fit but finally managed to get the ends past the delta ring. In hindsight I probably wouldn't have scratched the delta ring if I had shaved the ends of the handguard with a dremel.

LAR-8 Carbine extension tube measures 1.182 OD. Magpul mid-length installed with no issues. RRA does post a warning about other hand guards and the thread mis-match for their receivers. At lot of AR stuff will interchange but defer to their CS for confirmation. It is a great rifle, and it too can be 'barbied'.