anyone know what Alex's rig was at this time...

I don't know his amp, but I am fairly sure he used Gibson ES335's and he had an EH Electric Mistress.

Alex used a lot of reverb, and chorus. You really don't have to duplicate what he had, because he had a lot of rack stuff, very expensive, and it wouldn't sound like him, because it was setup for a live concert sound. He uses Galien Kreuger heads, so that could help you a little with his sound. The thing is a lot of what you hear are effects, like chorus, flange, reverb, delay. In the 70's he hated the clean sound he finally started using during the early 90's, namely Presto. He used very lite overdrive or sometimes some fuzz, but not much of a crunch sound, mostly just a little extra off his amp. He used that Gibson, he also used a Les Paul Standard. If you are listening to stuff off of a live album, say Show of Hands, he used custom Canadian S type guitars. In the 90's of course he has been using PRS.

Al used alot of gibsons, les pauls and 335 or 355. liner notes and stuff said that he used highwatt and marshalls. but rumers said that he had everything plugged into a fender jazz. regardless, one thing that i came across that will get you that sound from Caress of steel, a farewell to kings, and hemispheres (Sort of) is to turn your volume on your guitar down about half way. it's not very practical, and doesn't really work live, but it's alot like his sound from then.
also remember, alot of the stuff he was doing back then was doubled be an acoustic. that adds to his sound too.