If you’re building a rifle for YOU, get the action that makes the most sense to you.  For a custom, it doesn’t make a nickel’s sort of difference whether you start with a new or pre-64.  MY preference is for the pre but that’s what I sort of grew up around.  I also prefer the 70 safety and trigger.  For the latter, if you set them right there isn’t a better hunting trigger.  Both of these actions may require some tinkering to get right but it will be minimal.  
Good luck on your build.
				
			Good luck on your build.
	








