Regarding the tachometer: it's just the other way around. IF your engine is NOT equipped with a rpm signal, it's common to use a signal from the alternator.
Regarding parts: I have ordered once from summit racing and received parts within 7 days from Ohio to Germany. Shipping 100€ though, because of heavy parts.
There are a lot of old US Ford trucks in Norway, my guess would be there are parts available also.
Regarding alternator: check for the correct one! There are different ones possible with different mounts.