Yes, you should get the ecu with the 7m, and the engine side wiring harness. The 22re ecu wont be able to work with the 7m, since it has two more injectors and 1 more knock sensor. If you can get an entire wiring harness it would be the best thing to do, I am not sure if your friend's 7mge harness has all the extra sensor wires for the 7mgte, and I believe he needs the 7mgte ecu, since the ecu has to deliver a wider range of fuel to the turbo engine than it does to the N/A. If he can re-use his 7mge harness, you should be able to pick one up from a wrecker, or off of one of the Supra boards such as Supraforums, or Supramania. Also the Cressida came w/the 7m, so you ar not limited to getting one off of an '86.5-'92 Supra.

Here is a link to a 1990 Toyota Supra Factory Service Manual, for your swap.