[Vwdiesel] alternators

[Doug]

I have a 1981 Caddy diesel that I don't think is charging the battery 
enough. I have a parts catalog from Detroit that has new alternators 
available in 90 amp versions only for diesels. My local parts shop says 
all of the 1981 diesel alternators were 65 amp. The one on my non-AC 
Caddy is 65 amp. Can I install a 90 amp alternator w/o any other 
upgrades or modifications?