The 100-300 is certainly worth looking at - in referring to the range of the zoom I really meant the range of focal lengths covered. 100-300 is a fairly modest 3x range, and in an "easy to design" focal range. Lens ranging beyond 3x get a bit dodgy.
F5.6 is a little on the darkside by current standards, but this is offset by smaller size and price.
Having said all that, if I were re-equipping with FD
glass, I think I would go for the 70-210 zoom, and look at a prime 300mm or 400mm - Sigma made some excellent long primes for FD
, and these should be a real bargain second hand.
This is an area where scanning the local smallads can reap rewards - I've often seen entire FD
outfits being sold for stupid prices (probably the result of an attic clearout by a non-photographer).
Colin K. Work, Pixstel