Pete, since the forks assembly on the bike now is from a heavier machine than your "cafe" Tonti, perhaps a slightly lighter oil might be better to prevent harsh dampening...Maybe 5 weight fork oil instead of the slightly heavier ATF.. I'm assuming the 45 mm forks were not under dampened on the original bike...
For those interested, the 45 mm later forks on the 80's Tonti frame bike look very nice, a more balanced look with the large Guzzi engine...The original 35 mm forks look like they belong on a 250cc bike in comparison...