You should be OK as long as you use a "long action" carrier group. Pretty much the only difference with a post mil E is the lack of the cartridge counter window. Probably need a bit of hand fitting.
^
Yes this ^! ...
The safety difference makes interchange between post-mill tang safety receivers and pre-mill internals a no-go because you'll have a firearm with no functioning safety. The whole sear assembly being the critical difference between the two. (I'd love to see the internals of one of those dual safety aftermarket tang safeties fit to a pre-mill though!)
Much as I hate to admit it, I have to agree with LBK on this one. At some point the tinkerbell effect becomes absurd, or worse, dangerous!
