Main issue is that you don't know who built it. Sometimes the various receivers require different dimensions and may have had work done to make operational, such as on the barrel shank for press fitting. Point being, stripping the parts from the gun would be a lot of work.
Rapid Fire receivers are the earlier ones -- current are AWO marked and those are known to have tolerance, heat treat, etc., issues across various platforms. I consider them to be rolling the dice. YMMV.
Personally, I'd send it back and buy what you want instead of starting a $1k plus project on this gun plus wait time...