Wow, where were you when I was single! Just kidding.
The Savage can take almost any large displacement motor. Here are couple of links for decent to upper end engines.
http://www.hobbypeople.net/prdcls/care2101.asp
http://towerhobbies.com/listings/cat-cat-g.html
Any of these would work that are .21 or larger in displacement, have a rear exhaust, and pull start. Read the specs on the ones you might be interested in and it should give you the details.
If you want to make him smile for a year, the newest bad boy that everyone seems to want is this:
http://www2.towerhobbies.com/cgi-bin/wti0001p?&I=LXLGH7&P=0
Shop a few other hobby shops for price, but if you can't beat Tower's price, then I would get it from them.
As to the other parts needed, all he will really need is an exhaust pipe matched to the engine. That gets personal. Why not throw in a gift certificate for another 50.00 so he can shop for the one he wants for that engine? I know that would do it for me, but I am easy to please, as you can tell, because I didn't wait for someone as wonderful as you!
Oh, on edit, just thought of this. If his current engine is pull start, you might want to consider getting him this:
http://www2.towerhobbies.com/cgi-bin/WTI0001P?&I=LXERF2&P=V
If he already has the Rotostart on his current engine, then no need for it as the old Rotostart will fit right onto the new engine. The old pullstart will fit the new engine, too.
