Finding a left handed rifle in a 70 express model is too expensive to make into a 404. So what would need to be done to a long action such as a 7mm rem mag to make a 404.

I have the 300 rum magazine box,follower,and spring.

I found a thread here that talks about the 375 style larger ejection port with the 70 express action. Would it be neccessary to modify the 7mm rem action to the same specs as the 375.

thanks in advance.
fast

I turned a Post-64 PF Model 70 in .300 WinMag into a .404J and had to change out the magazine box ("window" box from Brownell's) and follower and had Dennis Olson do the feedrails. An RUM box and follower "should" do it, along with the rail work. Dennis also opened up the ejection port at the front of the rear bridge.

You might also consider replacing the bolt stop and ejector with ones from an express action.