[260Rem]

Question:
Is a pre-ban AR-15 lower compatable with any of the new post-ban upper receiver assemblies? IE: Can an SP-1 accept a new match-type upper assembly? Or would I be better off just going and buying an entire match-grade AR?

Any and all help greatly appreciated. Hopefully there will be a clear-cut answer on this question. (And BTW, it is not a true SP-1 but an assembled-with-on-hand-components model, with the A1 forward assist bolt in place.)

[BallisticTip]

Yes you will need to get a offset pin adapter, like this.
pin (http://www.bushmaster.com/shopping/lowers/nes-06.asp)

[Atticus]

You only need the pin if the upper and lower have different size pins/holes (see link). Otherwise, pre-ban vs post- ban doesn't matter.

http://www.biggerhammer.net/ar15/uppers/