Joel Pendergraft has replaced the Remington bolt heads with a Savage on several of his actions, and one of mine. For both liability and cost reasons, I don't believe he wants to do it for a general audience. The reason I'm posting is that it took us about 7 hours to do mine -- we probably did more than you'd want; that time include sleeving the bolt, starting with a piece of 304 SS that had to be bored out. -- Hey. It was laying around. You know how it goes -- sure, 304 cuts hard, but it's only gonna be this one time . . .
Then I measured the timing wrong & "fixed " it (a tip: always measure the clearance just before the bolt hits the extraction cam, not when it is fully closed). Which meant we had to do some more work.
But the absolute minimum requires cutting off the old bolt head, measuring & drilling a hole in the bolt for the Savage bolthead retaining pin (better use a carbide drill), and redoing the firing pin to fit the new bolthead. Of course, you also have to buy the Savage parts, and sometimes they have to be trued. On Joel's rifle, the .308 head and the mag head had some size differences that had to be made common.
For your project, all in all, with the cost of a new Remington bolt plus the fitting, or a conversion to a Savage bolthead(s), after already paying $250 for the old Remington, I think a Predator Action (Remington drop-in) from Jerry Stiller would suit you much better, for more or less the same amount of money when all is said & done. He advertises a left-left configuration; have no idea if he has any on the shelf.
Starting with a Predator, I'd bet Mike Bryant would do the rest of your work. That too would be a plus.
