it all depends on how you do it. i converted my x 4.6 to brushless. there's a cheap way to do it and there's an expensive way. i went the cheap way, so i may be able to help you.
first of all, hobbycity.com is your friend. you can get lipos there for less than cheap ni-mh packs. the turnigy packs are great.
also, you can get a motor mount from kershawdesigns.com. the mount is only $20 which is a steal for what it is.
http://hobbycity.com/hobbycity/store...em_2350Kv/150A
this esc/motor combo works great for the savage. the esc is good until 6s lipo, but the motor spins very fast and is only good up to 4s lipo. it shows that it costs $190, but it is $150 once you log in. that combo works well for savage and revo conversions. the esc is better than the MMM esc as long as you don't mind the esc's huge size and the fact that you have to be careful when programming it as 0 timing will fry it. if you leave it at stock setings, you have nothing to worry about.
http://hobbycity.com/hobbycity/store..._20C_Lipo_Pack
those battery packs will work nicely. i used velcro to secure my lipos. that is the hardest part of the conversion and needs a little creativity.