Jon:

On the Magnum XLS 40 and the Magnum XLS 46 all dimensions, except the cylinder bore, are the same. Other than the piston and liner, and ignoring the "40" or "46" cast into the crankcase, all the parts can be interchanged freely. In fact, other than the p/l, head, and crankcase they all have the same part numbers. I don't know if OS has the same commonality in the 40 and 46 FX engines.

Measure the outside diameter of your cylinder liner. The Magnum and 46 FXare 1.000" diameter. If your 40 FX is also 1" diameter there's no reason you should not get the XLS 46 liner and piston, get a little hop-up along with a better, less expensive, piston and liner.

The part number for the XLS 40 P/L is S40203, the XLS 46 P/L set is S46203. The wrist pin is also shown as different between the 40 and 46, I suppose it's just length since they both use the same connecting rod, so if you go for the 46 order also the 46123 wrist pin and retainer. And as a matter of course, the head gasket S46112. THis number works on both the 40 and 46 engines.

And yes, these parts are available from Hobby People, they are the inporters.

Note: The cylinder heads show different part numbers also, but one will bolt in place of the other.

Hope this helps.

Bill.