I believe Fulton Armory and Bushmaster uppers are compatible with DPMS but don't take that as gospel. Just something I remember from when I was researching various .308 AR platforms a few months ago.
I can tell you fulton armory uppers are very well made and mated well with my LR-308 DPMS lower. I think they are the best bet since DPMS know makes multiple 308 upper with changes in their rail height.