Hi Adrian, Mini Infernos are less than stock lol. Parts that are neccesarily upgradable to handle the brushless system are the following:
1. CVD's
2. Ball diffs
3. I would get alloy dog bones for the drive shaft
4. Bearings
I disagree with Jaydin that temperatures in the small high kv rating brushless motors is an issue, and even if it is (which I know it isnt because I ran my C4 dynamite insanely hot that it split my skin when I touched it but it still was not hot enough to thermal) just use the lower gearing ratios which I prefer using with the Tekin system anyway. I have driven a car with the system and it is very very very responsive and has insanly controllable speeds.
Good luck with your testing of motors and such.
Just a little tip, parts that are perishables such as A arms and shock towers imo should be kept plastic because its cheap to replace. Alloy is a problem because if you crash hard it will bend, leaving you with a ruined shock tower AS WELL as a a bent shockshaft (I have learnt this the hard way). People say get carbon fibre shock towers but they are probably only slightly stronger than plastic, but it has no flex, so when it breaks, it shatters, and costs alot more than replacing a plastic shock tower.
Jerome