If the receiver of the SCAR is NOT engraved with your SBR maker's mark and the engraving is on the 10" barrel, sell the SCAR. It shouldn't be very difficult to sell because you have a Belgian make SCAR, even though most people prefer the FDE color instead of black when it comes to SCARs
Once sold, buy the NRCH SCAR 16 this time around OR stick to ARs, I can't tell you which one to choose.
However, I would NOT buy a SIG product, unless it's SAN SIG from Switzerland.
If the receiver is engraved, you can buy the KIT and keep the original bolt as spare parts, or sell the whole rifle, whatever you choose between those 2 options doesn't matter because you'll be taking a bath on it financially because people pay way less for rifles with the receiver engraved already that cannot be changed.
Guns that the receiver cannot be changed like CZ Scorpion, SIG 550, SIG Mcx, etc.
What ever you decide let us know because we're curious.