The 114 [ 250 ] diff. is open axle and will not fit. Your's is enclosed swing axle and
rather difficult to change ring and pinion. They are available at any decent salvage yard
and can be found for short $$$ as they were in many 60's chassis. The ratio is stamped on
the side case below the drivers side axle
tube.
After changing it out , it is important to centralise the unit via the cross strut. I
believe the offset on that model is 42mm.
I have a simple measuring tool design for these that I can send if you or any others need it.
E-mail me for particulars.
Arthur