Condenser / lamp distance

[richard ide]

I am using the head of an Opticopy camera/enlarger for 8" x 10" enlarging. It has both point and diffuse light sources and an amazing set of condensers. The beast was designed for using a 360mm Componon S. I do not have the electronic package for control, and access to the track the light socket is on is a PITA to use in the dark.
Can anyone give me a formula for calculating lamp/condenser distance for a particular magnification ratio. I have enough room in my darkroom to enlarge up to about 40X.

Thank you