Check out his Althea and listen to the tone of the solos. I believe this to be about the "dirtiest" clean tone of the 80's. I believe this tone to be the MC2300 pushing the JBL E120's "too hard". I don't think this is any kind of pedal overdrive. It may be the Twin driving the Mac a little more than 1982 or even 1984. I love this tone though.
I am a hardcore Althea fan and 83 has a few of the best, and Ive also really loved Jerrys cleans during this time when he was playing well.