I just bought a bushmaster AR 223. It has the upper with the handle. Where a good place to get a upper with the slide for a scope? Thanks for info

You are looking to change out a carry handle upper for a flattop, or looking for a complete barreled upper? You have 2 options to just change the upper receiver itself, buy a stripped flattop (A3) upper and reuse your existing forward assist assembly and ejection port door/spring/shaft (these range from $60-70) or you can buy an upper with them already installed for $90-100. It's not very hard to swap them out, but you do need at the very minimum a good armorers wrench, and I'd highly recommend an upper reciever vise block. although I have successfully changed them without one, You run the risk of cracking the upper reciever on the thin lower portion of the ejection port, along with marring up the finish on the upper itself. I'd check out Spikestactical.com, PalmettoStateArmory.com & AIMsurplus.com. They all have good quality parts, and I have bought from all 3, excellent companies to do business with. I don't see where you are located, but If you are close, I can change one out in about 10-15 minutes.

Richard..... Does head spacing issues come into play when changing the upper receiver (not the complete upper)?

No. The bolt headspaces inside the barrel extension, and swapping out just the upper is not a concern, since you are still using the same bolt & barrel.

check out bravo company. That's where I got myA3 upper when I swapped.