I don't think I read it, but what wheelbase is the 240Z setup for? 210mm or 225mm?
I downloaded the instruction manual from HPI Europre (74MB); the 240Z and 510 are both 225mm wheelbase; the AE86 is 210mm. The difference is in which way the lower control arms and upper shock mounts are facing.
Also, a word on the front shocks. The front half of the front diff case is the piece that determines which shock configuration you use, so it's a little involved switching from one to the other; this is not a presto-chango thing.