overkill is using a cannon to kill as mosquito.
an RB26DETT in a datsun, well thats just like using a nuclear bomb to kill a mosquito.

altho it wood be good to see you do something different. id say go for it. the gearbox on the 26 is different to the one on the 25's so it might take a bit more work to get it in (you can always swap back to the stumpy from the 25). the engine is much the same as a 25 (just look at all the r33 gts-t's getting around with a 26 block).

if u did go for it id ditch the sequential twin turbs and go for a single huffer (easier, less space in engine bay taken up)

there would be a bit of work in getting the 26 block to sit on the mounts in the bay.
new cross member and gearbox mounts mods too. then u need a tail shaft, diff, wiring, fuel....... life insurance