what is the difference between a PK6 & PF6 Gearbox

Hi There I hope you guys and girls can help I have a PK6 box and a PF6 box in my van and I am hoping that there is not much difference so I can put the pk box in my van as the PF6 box is missing sixth and second is noisy.

Any help gratefully received.

what is the difference between a PK6 & PF6 Gearbox