a big fork'n gamble

I have bought a fork from Germany (ebay). It is from a PK 50 XL2.
In order to have a sixties scooter that doesn't dive under braking, as well as the ability to add a disc brake, it is common to add a pk fork. 'They' say that to do an 8 inch wheel to 10 inch wheel conversion you need a pk125 fork, but NOT a pk50 fork. I need a 10" to 10" conversion, which (apparently) needs a PKXL 2 fork.
I have taken a punt on the 50 being the same as the 125 in this model. It should arrive sometime next week, so I'll let you know.
Oh, and just to rub salt on the wound, SIP scootershop has just put PK conversion forks back on their catalogue. At least there is a (albeit expensive) solution available if I have the wrong part.