Thanks Albert, that is exactly what I needed to know. Only reason for me getting the old F9 was to replace one that had been given to me back in 1976/77 it had since been lost due to some missing things from a military move. I had tried another manufacturers 'F' unit but it too was about 1/4 inch short in length. Think it would look a little odd with extended couplers as the trucks themselves would be too far in from the front/back of the loco shell as you indicated.

Thanks again, much appreciate the test fitting you did.

Thanks for the reply Acy. Guess I asked the wrong question though.

So, does anybody know if the old F9 shell from about 1975 is the same size (length, width, internal height clearance) as the newer 2013 F7 shell?
If they are the same, it would save me the effort of trying to retrofit the older frame to accept a decoder and avoiding any milling that might have to be
done. Just looking at an easy out as it were, if they are not the same size, will just mill the old frame sparing me the expense of a newer one.

Thanks again