Essential: brass T-plate, brass gearbox brace
Very handy: new motor plate
Handy: shock towers
I'm using the JC shell and liking it

Weight wise I use the homemade steel T-plate (soon brass one), 80gr of lead on back half of the battery space, 25gr left of motor and no weight up front. With this set-up I reached about 65,2% of weight on the rear wheels.