My first attempt would begin with a GE Center-Cab Engine from AHM. I like this model because the molding is crisp, and the small motor and drive train allow for a really tiny conversion. Here it is as it came out of the box.
I began by shortening the chassis. Here you can see the small size of the motor. The motor in AHM's Plymouth Diesel seems the size of a soup can in comparison.
The engine deck as-is.
The over-size railings were the first to go. Then everything above the surface of the deck, except the 'U' shaped piece that holds the sides together. It is also the only connection point between the deck and chassis. You can also see I removed quite a bit from each end. Strangely, the deck is not made of styrene, but rather some sort of acetal plastic, requiring the use of super glue. The joints were pretty fragile, so I used some styrene channel to give more glue surface as well as hide the seam. This reinforced joint is nice and strong.
In altering the deck, I damaged a lot of the molded-in tread detail, so I covered the entire deck with a layer of Plastruct tread-plate. You can see I added a 1/4" extension under the right end, this to allow a walkway around the rear of the engine.
Now it was time to attack the body. First I removed the short hood. Next I covered the opening with .030 styrene and filled the four holes with plugs. Then I removed the end of the short hood right behind the louvers, and ended by narrowing that piece.
Doors made from .030 sheet and brass wire. My next conversion (yes, another is on order) will use pre-made custom doors.
This short, narrow hood is necessary to cover the hole in the styrene end that allows clearance for the motor.
Now to the long hood. I buy the common size grab irons, especially these drop irons. I removed the molded on grabs, and used a BLMA template to drill the holes for these. A little trick is to use a styrene strip to hold them a uniform distance from the hood, while you super glue them from behind.
Ahhh, perfectly spaced. I also remove all the molded on details from the top of the hood, and sanded everything smooth.
When I need non-standard size grabs I use this, the Grabhandler. Kind of pricey, but there's no denying it is perfect for the job. And once you have it, you'll look for places to add grabs. These two are for the top of the hood.
And here they are installed. I used the styrene strip again to get the proper standoff.
That's all for now. Next up is railings and more grab irons. Thanks for looking. Don