>>63913027
That should work in theory since there's no reason to upscale the fire control, but you'd need hands on the lower with calipers to verify unless the manufacturer publishes the dimensions for whatever reason

>>63913040
Correct, it doesn't even have to be per mil spec. Milling the selector bearing flush with the "shelf" .450" deep and a .950" relief for the auto sear "dog leg" would suffice [DS Arms does a similar thing with their lowers]