I picked up an unfired DPMS Slick side 308 with the 3/16" upper at a very good price. Thinking about swapping out the upper receiver for one with the dust cover and F/A.

I have a AERO M5 and tried that upper for fit - was not happy. It was too snug at the take down pins and the gap between the upper and lower looked crappy.

Has anyone tried any of the other LR-308 upper with a DPMS lower and did it fit correctly?
What about a rail? I am partial to the UTG Pro USA made Keymods (MTU020SSKC) but am not sure if the locking lugs will fit correctly with all the variations on the upper receivers (forged, billet, etc.) Brownells has the DPMS version but at a high price.

Or just sell it and stick with the SCAR17S and AERO.

I have done it but with a DPMS upper, not aero to dpms. I like the Guntec Rails, they fit just fine on a recent rifle I finished.

I have a Fulton Armory upper which mates up perfectly to my DPMS oracle lower, and a Fulton lower which mates up perfectly to my DPMS upper.

I don't run them that way often, usually the Fulton is on the Fulton, and the DPMS is on the DPMS, but when I do pull a switcharoo they both fit together fine and run flawlessly.

The Fulton uppers are of the DPMS "low" gen. 1 pattern.