Since my original post I did some more research and found one video in particular on youtube where someone did something very similar and it looks like it is possible to re-use the original trigger guard (which, by the way, includes the bolt release) but I would definitely need to use a different magazine attachment system.
The problem is that on the Trophy Hunter XP, like mine, the mag is held in place by a plastic clip on the front of the mag and a slot for that clip that is molded into the bottom of the plastic stock. The Boyds stocks are designed to use the older style metal bottom plate that has a spring loaded clip that holds the mag in place. So I think in order to use a Boyds stock you need to purchase the metal bottom plate as well as a "plain" bottom for the mag that does not have the clip on the bottom front like the one that came with the gun. You can probably also just purchase a complete, older style mag. Once those changes are made it may even be possible to use a larger capacity mag since you would no longer be restricted in length by the need for a clip on the bottom of the mag.
Next question: Does anyone have a Savage part number for the older style metal bottom plate assembly that includes the spring loaded clip?