A freelance 00 side tank locomotive body that fits on the Hornby 0-4-0 "Holden 101" chassis. The Caledonian Pug (Smokey Joe) chassis may also be used (it is identical) but the Holden 101 is recommended because it includes a weight that fits in the smokebox. These engines are readily available (in good condition) second-hand. Do not use Hornby's inside-cylinder 0-4-0 chassis.
In the photographs the side tank body is shown mounted on a chassis, and alongside my Holden 0-4-0 (nearly 40 years old, and somewhat the worse for wear).
To remove the original locomotive body from the chassis, work plastic strips or wedges between the cylinders and the valve chests. It's better not to use screwdrivers, which can damage the plastic.
To put the new body on the chassis, position the back end first. The chassis has two hooks behind the motor, and these attach inside the firebox. Then push the front end down until it clicks into place, taking care to keep the connecting rods inside the cylinders.
I have successfully mounted the body on three different chassis of varying ages. You might find that the loops on the end of the motor retention springs get in the way, in which case you could trim them with wire cutters or bend them out of the way (but this has not happened to me). Apart from this, there is no need to modify the chassis. There will be no difficulty in removing the new body and putting back the old one.
The model can be spray painted, or brushed with several coats of thinned hobby acrylics. Gloss acrylics are more durable than matt acrylics. After painting the glossy finish can be flattened with a coat or two of semi-gloss varnish. The surface is too uneven for any of the conventional lining techniques, so I have used masking tape and a metallic gold acrylic pen. I have also had some success with waterslide transfers.
I chose White Strong and Flexible (polished) to keep the price down, and although the detail is a little crude and the surface a little uneven, I am very pleased with the overall result and I hope you will be too.