According to the manual there seem to be slight electrical differences between the two which I guess would not matter, but are they the same size with same mounting brackets etc ?
Yes higher output from the 1098 dynamo, and I think the regulators have different part numbers. You might find that the shunt coil overheats, if so swap the regulator as well.
The difference is v small - it won't matter - but an upgrade to alternator is the one change I think is almost essential for a Minor that's in any kind of regular use. Not expensive - pick them up at autojumbles for £1 !!