Well if I am not mistaken the F4W60F is the early gearbox for the E10.This box was not the strongest,so the F4WF60A box came as a stronger replacement,and also bigger driveshafts were used (can't remember breaking one of those).As far as I know only the F4WF60A was used on F10. An easy way to recognize it is the reverse switch facing the front of the car,near the oil filling plug.This box will handle an A14 without problems.I haven't done it myself,but I was told it was very easy to put a 5 speed gearbox in an E10,so why not in an F10.But if I was to do it I would try to get as much parts as possible from the N10,like the driveshafts,gear linkage,first part of the exhaust and this kind of things,just in case........As for the free play in the gear lever,there are several pivot points in the linkage,and the plastic bushings in there can wear after some use (supposing nothing is loose,broken or missing in your linkage).If you plan to restore the car and take the engine/box out anyway,also take off the subframe and the rear suspension arms.These things can rot badly and are more and more difficult to find,thus more expensive.So protect them VERY well.Shouldn't you know it already there is a club in Norway,the Norwegian Datsun/PMC Register (link to it on the English website).You might find some help there also if needed.