Remember that if you are going with a big single, you are going to need bigger fuel injectors. With a J-Spec Aristo/Supra, you have 440cc high-impedance/saturated injectors. The "export spec" 2JZ engines had 550cc low-impedance peak/hold injectors [generally higher quality], and actually have the flow capacity to support the smaller single turbos.
If your hp goals are under 500hp [crank, not wheel] you might get away with wiring up an injector resistor pack from a US spec car and some US spec 550cc injectors, with an AFC of some kind to supplement. Any horsepower goal over that and I'd really recommend a stand-alone, and bigger injectors are a must [along with fuel pumps - but you can twin in-tank MkIV Supra pumps or some lil Walbros for nice flow at a decent price].
As far as other suggestions for maintenance/things to do during/before the swap? I'd buy a short shifter of some sort for the tranny, drain the tranny fluid out the bottom, replace the bolt and then you can fill it the easy way from the top while you are replacing the shifter. Treat her to some Redline MT90.
Wiring - measure twice, cut once.
I guess since you are going single you don't have to bash any of the firewall, so that's good.
Buy more tires?