http://ponymotor.embarqspace.com/
I emailed these guys last night, to ask how their system works, they sent me the following picutes. Seems they connect a starter to the starting motor pinion.
Here is the reply they sent...
"Alan... See attachment picture's....You remove the ponymotor clutch,send it to me,I attach a 12 or 24 volt starter to it and send it back to you.One picture is the ponymotor clutch, one is of a starter attached,one is installed on a 9U D-6...The conversion cost $1,200.00 plus shipping for a 12 volt and $,1,300,00 for a 24 volt.. We also have a cover plate and gasket that goes where the ponymotor was,, The plate is $129.00 and the gasket $18.00....This is the cost as long as your ponymotor clutch gear and disconnect assembly are in good condition... Thanks Bryan Parker"