257 AI is a favorite of mine; I'd leave it that way if I were you.
Have you checked out the CZ actions available through Brownell's:
http://www.brownells.com/.aspx/sid=7170/pid=1849/sku/30_06_Length_Action?
The other thing you could do is grab up a Zastava rifle (Remington 798) as donor? Grab one in 7mm Mag or 300 Win Mag and you could probably get a few bucks for the take-off barrel to fund the project, and I think they have decent triggers, though for a DG cal like the 375 Ruger I'd go w/ the shroud-mounted M70 style safety.
Its worth a try, and lets you have your cake and eat it too
!