G'day gml,
No reason why not.
The only consideration is the cutter clutch arrangement. The 28" is probably from a Tractor model which had the clutch mounted behind and seperate to the deck. The 30" is probably from an anniversary or evolution model (?). The clutch on these had components that were mounted on the deck. No real problem, just means you need to drill a few holes in the deck to mount these components.
I'll do a bit of research......
Cheers,