I would call a 3.9 kickstart an 3.1 ROM with the 3.9 updates applied to it 
Than you would call a 3.1 ROM a 3.0 ROM with some 3.1 updates and a 3.0 ROM a 2.0 ROM with some 3.0 updates...
I'm quite happy with the
1MB 3.9 ROM's I made for my A3000! :cool:
