this is my opinion on what is "must have" from your list:
steel gear set, 39t for bigger track, 40t for smaller track
front universal shafts, rear optional
tuned pipe, not sure what you mean by 5.2 or 7.0, stinger diameter?
the rest i think is not necessary but nice to have. hey christmas present to yourself. why not.
add to list:
optional steering rack with 2 additional ackerman holes
i just finished building my kit, haven't had a chance to run it yet so i don't have first hand experience of its durability. should be ready by this weekends race.