i have a customer that has a d7-3t he wants to convert to electric. the pony motor hole doesnt have a standard mounting pattern.do i have to machine the housing to accept starter?any help is appreciated.thanks

What serial # 3T is it?
Early 3T1-3T4389 units had a three bolt attachment at the bell housing, later units had nothing but a hole.
Either one requires custom work.
Early ones can be made from a standard starter nose.
Later units require fabricating an adapter plate to mount to the bell housing.

I don't have a lot of info on these even though I've provided what I have. Seems no one will share the results of getting one installed.

the serial is 3t12440

Built in mid 1950. catskinner