Most any 1st generation EMD sound decoder will work. I put a Soundtraxx LC (“low cost” decoder) and a 1" speaker in mine…well in my case I put it in an E7B. I put the speaker and enclosure in the space where the cab would go. But there should be plenty of room in the A unit too. Last I checked the LC’s run around $50 or so.
I’ve put Soundtraxx LC decoders in several P2K E units. The Soundtraxx decoders only have the bell, horn, and diesel sounds. But if you don’t need the other sounds, coupler clank, brake squeal, etc, Soundtraxx has far and away the best EMD transition sounds. Other decoders just take an idleing EMD 567, and pitch it up as the throttle increases, with no transition. On a couple of my units, I put a second speaker in parallel, in the B unit, connecting the units with a Miniatronics mini connector. The Soundtraxx doesn’t seem to have any problems running two speakers.
Ya I thought of that after I posted it, the Soundtraxx one is only for one motor so is more correct for a GP or SD or F than an E-unit. That being said, I’m not sure everyone would be able to tell the difference, especially if you ran an A and B unit together (or an A-A) unit and had sound in both. If you shop around you could probably find two Soundtraxx LCs for the cost of one LokSound or Tsunami.
Going back to your original idea of placing a Proto shell on the BLI:
I had a BLI E8 and wanted to put a Proto E8 shell on it rather than repaint. I realize your situation is a little different. I ran into the door problem, but found it easy enough to remove the door hinges and just glue the doors in place. Then I looked at how to retain the shell on the BLI base.
The BLI E8 shell is held on by four flat catches that are glued into shallow channels inside. Fortunately, the Proto shell was slightly wider internally, and I was able to remove the catches and glue them inside the Proto. It is retained properly, and there is no bulge.
I also needed to change the chime soundfile from a Wabco E2 to a Nathan P3. Having a QSI programmer, this also was easy. Now looking for the right set of horns.
I have several MRC decoders, with the multiple engine sounds, SD60, SD70, Alco, and EMD 567. When I programmed them for EMD 567, there was no transition sounds, and it was a lousy sounding EMD 567, compared to the Soundtraxx.
You are right though, that the E units had two 567s. But an E unit, or two GP-9s sounded pretty much the same.
