My 2 PSA uppers only fit PSA lowers without modification.
You would also need to change out the gas tube to a proper length gas tube.
You would also need to change out the recoil system to a proper weight buffer and a proper spring.
I did not have to change the PSA's recoil system on the rifle lower I bought. Carbine lowers are a different matter.
You might also check out Bear Creek Arsenal. Their stuff fits DPMS lowers.