Ali SC3

iTrader: (10)

Pretty much any of them that will plug into a mk4 supra type ecu connector like some older aem units.
The newer ones you will need a jumper harness to go from ecu to the supra plug as they are more universally setup, but does retain most of the stock wiring still.

I would honestly advise them not to go standalone if their goals are under 500hp.
It gets so complicated and so expensive so quick, that if you have to ask the question what standalone should I use, you really need someone around that knows it from start to finish or you will be at the mercy of installers and tuners. So my advice would be to advise them to just enjoy it or find a good tuner who knows a good shop that can install a standalone and have them tune it.
It is a good idea to find your tuner first honestly, and ask them what they prefer, they will know which ones they did that ran best.
some prefer pro efi, some it will be aem, there are better ones also but really expensive.
On the other end alot of DIY folks like the emu black but requires alot more knowledge of everything.. but if your tuner and shop knows it that could be ok.

I have used aem but if they can afford it I would say a pro efi setup, jumper harness with all the extra sensors like flex fuel and a solid tune.
They should be prepared to spend another SC's worth of money just on getting it setup and to run as well as the original ecu, but if your power goals are up there standalone is the only safe-ish way to do it.