IF you decide to go with the traxxas big block kit (which you can use with a SB/1-8th clutch) then it's like $35 BIN on ebay, or $50 at the hobby shops. Comes with a forward only kit too, so you would have spare tranny gears.

This will also allow you to drop a big block in when/if that day comes.

A SB with stock clutch WILL NOT fit the traxxas BB kit. Again, only a SB with a 1/8th scale clutch mounted. With that setup you would use the "mid-block" holes on the mount.

The mount comes with holes for mid blocks AND BB's