They do all work the same but the 7m intercooler has both the inlet and exit on the same side. The one for the 1j has the inlet and exit on opposit sides. If you were to use the 7m intercooler, then you would have to do some extensive plumbing to get it to fit. If you look at how the 7M is set up, you will see that the pipes from the turbo and the pipes going to the intake manifold come from the same side of the engine bay because the 3000 pipe is located over the engine. On the 1J & 2J, the intake manifolds are pionting torwards the front of the car. The pipe coming from the turbos goes in on the left side (looking at the front of the car) and the pipe leading to the intake comes out of the right side of the intercooler. So... The 1J intercooler flows from end to end. The 7M flows in one end and out the same side. It can be done, but like Van Diesel said, "the piping would look like an octopus".
If you are having trouble finding a stock 1J intercooler, I have one for sell and will be more than happy to sell it to you. Let me know.