alt/fan interchangeablity Q....

[gungadin]

OK...
I have a '76 with a '79 3.0L engine.
Whoever installed this engine retained the 5blade fan.

Here's what I think I know.
'76 fan is 245mm diam. (5 blades BUT the most common diameter)
'79 fan is 226mm diam. (11 blades and the smaller dia.)

I'm about to try installing an 11/245 fan in this housing I have.

Q: Should I be able to do this without changing alternators or housings?
Q2: Any other piles of @#$% that I might be stepping in?

Thanks friends!