Any of the GoldenLion (SH Engines) .28ci engiens would be great for the Savage. There are dozens of SH resellers, and many of these resold/rebadged SH engines have found great homes in Savages. The common SH resellers are LRP, STM, Mach, Werks, Dynamite, (the list goes on, ther are too many SH resellers for me to remember).

By far, the most popular SH reseller that has found its way into Savages is the LRP (at least form what I have read to date). The SH-LRP in particular that is decently priced but leaps and bounds over teh stock HPI engine is teh LRP Z28 Spec3.
To show you how popular thi resold SH engine is, just type "LP Z28 Spec3" and you will get dozens of links with hundreds of posts talking about this engine.