Hey, I go on holiday and come back to a section for decent dukes at last!!
As I have a 92 851 a 93 888 (lucky me!), both of which have been in bits I agree with the above.
The 851 has the P7 ECU, but a P8 (with the appropriate chip) will also work - ie the loom and injectors are the same.
About the only major difference I have found apart from the colour of casings/covers etc is that the 888 is supposed to have the bigger front wheel spindle, although mine has black rims and the smaller spindle.......
Things like under/over slung rear calipers seem to have been more a case of what was around rather than exactly what model or year.......
cheers
Paul