You have to grind off some of the frame to make room for the decoder. I found that a hard-wire decoder, like a DZ 125 (or whatever number they're up to now...) works pretty easily.
Here's a shot of a similar FA-2 install. The B unit is easier, because the chip can lay where the cab would otherwise be. (That's the one in front/right) On the A unit, shown to the left here, take off the big chunk at the rear of the frame. It's a bit more than you want to use a Dremel for, I always cut mine on a band saw with a good metal blade.
Lee
