Hello to all "Erika" enthusiasts!

I am creating "virtual museum" about mk3 and mk4 Escort, so, i am collecting a lot of data.
I know that there are a lot of differences between early and late mk3 Escorts, that could be seen in parts catalogues and when you compare different year cars in nature.
But i still have a lot of questions, that could be answered probably only by experienced ones...
1)There is difference in suspension (front have different mounts, but rear have different cross-member) - how these changes influenced cars handling?
2)It seems, that early cars had better quality steel or paint (there are more early cars on sale than late ones) - is this the case?
3)There are differences in gearshift mechanism - is it possible to put 1985 5 speed gearbox in 1981 or 1982 car with 4 speed?