I am a mechanical novice and after changing seals and the fan I have now re-installed and now find a vibration from the fan housing..!!! I was careful to tighten up as per Haynes etc. I did however replace fan for an earlier fan with conical middle and allen bolts....Would that make a difference?

The fan is typically part of the rotating assembly balance job. If you swapped out fans you probably introduced and imbalanced part in to the rotating assembly. Put the old fan back and see if it goes away.

with luck, it's just sucked in a paper towel you forgot about...

Taken tin ware off and alternator.....Seems i have the fan located wrong

Please elaborate on " located wrong"

A lot of folks take their fans apart (remove the pulley from the fan to clean, blast and paint) and put it back together without realizing that it was originally balanced at the factory. I've been guilty of doing that ... once

If one wants to take a fan apart, always mark both pieces beforehand so it goes back together in the same exact position. Maybe that's what happened to the 'new' fan you installed

It should have a dowel and key to keep it indexed. Not sure how that happened...

Did you have trouble setting your timing afterwards?

Mike