Joe,
Even if it is only a 2 wire generator, you can't use the exception. 250-20(b) requires the system to be a grounded system. There is nothing in 305 that says it doesn't have to be a grounded system and if it is grounded, then GFCI protection is required. If its not grounded, it is a violation of 250-20(b).
Don(resqcapt19)
