Ok, so here is the view of the gearbox modification.
Its not exactly a direct swap, and does require a bit of work.
Firstly I have created some holes in the face of the motor plate to mount it.
I had to remove the original drive gear from the motor shaft as the new gearbox is driven by a plane shaft with a key way in it.
I have fitted a pulley wheel which I bought from RS to the output shaft of the gearbox allowing me to use the original drive belt.
As a result of it running on 24v it does generate alot of heat, so I have a centrifugal fan on the other end of the motor (not shown in the pic) powered by a small battery that I keep in the boot. This runs continuously and draws cool air through the motor. I also have a thermocouple attached to the fan outlet so I can monitor the temperature as Im going along. Typically it doesnt exceed 60 degrees.
As the gearbox is longer I have had to set the motor back a bit and put shims in under the motor clamp to hold it steady. I have also attached a torque brace to prevent the belt slipping.
And so far so good ........