I know this is an older topic but wouldn't it be easier to source a 29-spline input shaft for your NP205 ?

And I imagine you could get one built if they can't be found ...a buddy of mine is having a custom input shaft built for a D300 to mate it to some Mercedes transmission..we can do it over here, should be easier in the US :humm:

this wont work as the input bearing on the dodge getrag 205 is larger.. and the front adaper is different... now you could bore the 205 case out and convert it but it would be easier to just find a manual 205 from behind a cummins...