Order a D8t from a hobby shop at a track. Order everything you need to build the thing from that same shop. The insight you receive from them will be invaluable.
Or, at the very least, if you have to order the the car online, get everything else from a local shop, WITH A TRACK, that races 1/8th scale, or at the very least find a guy that works at a shop that actually races. Don't have Joe's planes and trains shop tell you what you need to buy.
The RTR truck will be fine for bashing, even driving on a track, but it will really show it's weaknesses when it comes time to race. The biggest of which is gonna be 7 minute run times from that 454. 7 min run times would ruin even the best drivers chancing of doing anything good in a truck race, where 10 plus minutes is the norm. Two pits in a 15 min race is no good. Hell, you will prolly run out of fuel in a 7 minute qual...