The Losi Conversion kit is crap. It puts all of the weight in the ass end of the kit and the motor mount is set up to be used with the stock 2 stage pinion and has very little room for adjustments. I would recommend the dudes racing motor mount, you can use the losi single speed conversion (it hasnt caused me any trouble yet) but the dudes racing one looks like its built better, and just a generic Tekno v3 or v4 battery tray mounted up in front of the transmission. This may cause you to have to remove the RX tray and find alternate mounting locations. I personally used a Tekin 1550kv truggy motor but found that I had to gear way up on my pinion to get the speed I wanted out of it. so if I were doing it all over again (I bought the Losi kit originally) Id do those things and Id go with something closer to a 1700 or 1900kv motor so i could use smaller pinions. The LST2/Aftershock wasn't made to handle the power of brushless electric motors and as a result I've had to do a lot of hop ups to my LST2. Heres a list of what I can remember off the top of my head.
Aluminum Steering Knuckles
Lunsford Titanium Turnbuckles.
RPM A-Arms all the way around with Lunsford links for the upper arms
Heavy Duty Diff cases
Aluminum Shock Towers
Aluminum Chassis Brace
Aluminum Bell crank
The top 3 are mods Id personally recommend while you are doing the conversion. The Heavy duty diff cases I would also recommend up front but thestock ones will last awhile before they get chewed up inside so it could be done a little further down the road. The last 3 are upgrades that I did but I've only broken each of those parts one time a piece so you could keep those as stock if you dont mind periodically replacing them.