You didn't specify scale, Atlas and LifeLike (Walthers) offer them in N scale.
I seem to remember Weaver offering them in O scale, haven't seen any in G.
That looks like some challenging kitbashing. I don't think I'd waste the money on a BLI unit since you're going to gut it anyway. I don't think the sound decoder and DCC decoder will fit with the Blueline motor anyway. You should be able to pick up an Athearn SD-9 from e-bay for $25 or so for a junker. All you really need is the frame and trucks and those are reasonably accurate on the BB SD-9's
Since the only details you need are the side sills, fuel tanks, and trucks, it's more than good enough. The vent detail on the side sills is actually quite good considering how old the castings are.
Anybody out there knows who makes the SD9's or where can I find one, it can be an undecorated SD9 as well.