Eric ,What about that 280 pulley is it larger?

About the Diode:

Radio Shack does not carry it

MarVac does - their part number NTE506 costs a whopping $1.65

Fry's Electronics also carries it.

About the alternator:

The S130 pulley is no more than 1/16" different in diameter than the S30 unit. The difference lies I think in the Alt housing which does offset it a bit more from the engine. I tried to reuse the L24 fan/alt belt but it just wouldn't work - thus the S130 non-turbo one.