I’ve moved electronics to new tenders a few times. It can be a little challenging if a smaller low side tender as some of the ps2 board stacks. Can be a little tall but it usually can be done. I always keep the same electtocoupler that came with the electronics as some are different and can damage the board.
i think the fef is on the same chassis as the railking daylight and nw j so about the same length.