I believe you need the extended chassis kit to put the .46 in a Savage.

I have installed a Mach .28 and an SH .28 (same basic engine ) a Wasp .27 and several Fantoms...the only thing you might have to do is open up the holes in the (purple ) motor mount plate just a little.

The Mach .28 works well...and all the stock clutch parts will fit. Get one with an SG shaft.