Yeah I worked out that my 4age had been in 3 cars before mine.
My loom was pretty stuffed but I managed to fix it, there was a serious amount of unneeded wires also.
I would never bother with a RWD loom as it will hardly be much better.
They e-manage will help with power in the long run.
I just pulled the ecu end of the loom into the engine bay, and tested the connectivity from the plug of a particular (dizzy for example) and the pinout on the ecu. Its a easy job just takes time.