It is fairly well known in the American OO community that the Mantua/Tyco 4-6-0 is actually a 1/76 scale model, but gauged to run on HO track. The tender and boiler are correct for OO, and even the cylinder block is wide enough to work with no modification. The model is based on Sierra Railroad No. 3. 

I was never wild about how that model turned out. It ran OK but the drivers just seem so small. Then recently I had an idea. I have some spare drivers which I think were made for Bill Johann as part of his 2-8-2 project by Mantua. They are too big to fit on the model as a 4-6-0, but if you leave the front driver off entirely you get this I think rather successful model.

The cab, as noted in the prior article, is a Scale-Craft 4-6-0 cab instead of the stock cab. I wanted to give the model the look of an old engine still in use in the 1930s or 40s even. For an older time look, you can of course use the original cab.

Being really very pleased how this came out (I like the spacing and size of the drivers a lot) I am doing a second conversion, and this view shows the frame. I have another shortline 4-4-0 in mind, along the lines of engines seen in the classic book Mixed Train Daily, a favorite of mine when I was first getting into the hobby.

The only touchy part of the job is that you have to pull apart a driver and mount the original gear on it using a NWSL quartering jig. It ended up not being as difficult to do as I thought it might, which was encouraging as I have a number of steam projects backed up on the workbench.

I should note that Mantua/Tyco sold this same basic model also as a 2-6-0 and a 4-8-0. I had always liked the look of the 2-6-0 and purchased one of them as well. Alas, the setup of the drive rods is different and it would be a lot more trouble to get that all set up correctly with OO drivers. But the good news there is I can see a way to use that frame and the vintage Mantua/Johann drivers on another project engine, a 2-6-2. If I can get that one running by the end of the summer I will feel that I got something big done.