Hey neil_se and -Joel-, fundamently to get a fwd off the line well u need slicks due to obvious traction problems, u guys have a clear advantage over us obviously due to the car being rwd!
BTW my car weighs 1100 kg, a little lighter that an s13 but not much!
But back on to topic, i think it'd be nice to build a serious ca to run those times down the quarter, but i don't think u'll do it with the low quality imprts we inherentily get. Just in general the silvia being an older car it will have a few miles on it and hence be i porrere condition, i.e trying to obtain 12's may be a task without blowing up the motor or rebuilding urs. If u were to rebuild urs, and go the aftermarket ecu, fmic, 3inch exhaust, VL T3, Custom manifold and 550cc injectors, then u'd definately have a very quick car able of the times u want.
However the whole hassel of pulling the motor out and putting it back in which may make u think hey why not throw the rb in! Being a 6 the motor itself may be happier supporting similar powerr due to the fact that the same power only will be needed however it is spred of 6 cyl rather than 4 making it easier for u to mod it and not blow it up. Do the same mods to it as the ca, probably a t4 rather than t3 and it'll be a formidable street car!