Railhead Publications has begun selling a Sn3/Sn2 Center Cab Diesel Body. The body is designed to fit an older Athern, Atlas, Kato, Stewart diesel (on Sn2_Trains yaho group we have discussed converting Kato NW-2 locos to Sn2/HOn3). The body fits onto frame of the doner mechanism.
The kit is laser cut by Mount Blue. Actually, it is a scaled down version of the Mount Blue O/On3/On2 kit.
Current cost is $34.95 and is available from Jim Eakin of Railhead publications (P.O. Box 6579; Canton OH 44706) (to my knowledge, Jim is not on the web, so just send him a check)
This kit looks like an easy way to get started in Sn2.
Update (Jan 15, 2011): David Keith is in the process of assembly one of these kits. The body will not easily fit on the Kata NW-2 mechansim. It would require significant sanding of the weights to fit. As such, Dave has ordered an older blue box Athearn SW1500 kit, and hopes to use Jim Eakin’s techniques of MR Oct 1980 to regauge the mechansim. Will update when it arrvies.
Sn2 Trains 
Are these kits still available? I’d like one.
Chris,
The best way to find out would be to contact Jim Eakin. See contact info above. To my knowledge he does not have email. You could take a chance and hope he shows in Augusta for 2016 NNGC.
Dave K
Thanks for the reply Dave. I really should come out this year to Augusta and see the twofoot faithful. It’s been quite a few years!
C.
David, did you ever finish your kit? Would love to see the completed model.
Chris
Chris, I mostly finished my kit and had a review in M2FQ (or was M2FD). However, the overall loco is just too big for my liking, and dominates my Forney’s and #30 Diesel, so I have yet to complete the finishing touches.
Just to give you an update: The address listed above for Jim is incorrect. My letter to him came back “no such number-unable to forward”. Sigh. I really wanted to dip my toe into Sn2 with one of these.
Chris
Chris, sorry the address did not Sean correct. I just did a Google search for “Railhead publications Ohio” and got a plausable result. Another option would be to ask Gary Koehler for the address. I expect he and Jim interact.
Dave K.