Re: 270/280 question
I'm going to make some assumptions hers. I assume when you say the ujoints are the same, you also mean the yoke that goes onto the shaft in the flywheel cover has the same number of splines. I also assume that neither has trim. Now, the only thing that can be a problem is how the helmet connects to the top gear box of the drive.
There are 3 different methods of connecting the helmet to the gear box, look at them, they MUST be the same, and they are not interchangable. I't fixable if you still have your old drive, but it will take a certified tech to change the clamp ring.