That battery will work well.

For shocks you can just get the Tamiya CVA shocks, they're plastic but actually work pretty well. If you want alloy then look at the TRF Special Dampers which are great or Yeah Racing make some that are pretty good, especially for the price (about half the price of the TRF ones). I haven't used them but have heard good things about their "Shock Gear" range, which are their mid-range.

If you haven't bought the kit yet then look at the versions. There is a TT02D kit (not the chassis kit, a kit with body etc included) which comes with full bearings, CVA (plastic oil) shocks and a sport tuned motor. It has plastic drift wheels, but it may be cheaper to buy some new wheels for that kit than buying bearings and shocks for a base kit.

I don't know about the prop shaft, I haven't upgraded mine, the kit ones seem fine.

As far as servos go, I've gone for cheap JX 4409MG servos in my fun cars. They have similar specs to the Savox 1251 but are about quarter the price. So far I haven't had one fail. I don't think they are as precise but the TT02 isn't precise anyway so I doubt it'd make much difference. Servo saver 51000 could be an option if the kit one wears out too, its about $5 and they work well.

My view on this though is that it isn't worth spending a lot on these cars, buy the kit, do the basics and enjoy it for what it is. If you want better performance start with a better kit - TA07 or TB05 for Tamiya, or the Express XQ1S or similar from other brands.