retzev,
There were at least 3 Dallas cons during the 80s-- a 1984 Convention and Festivals(?) in 1985 and 1986 (also Newark during those years). In the final one, a nasty fight broke out at the hotel (witnessed by but not between fans), though I've only heard about it. JF, Millay and Terry Crawford attended that year.
Jim Pierson is from the area and you could ask him about turn-out, etc. too, and CrazyJenny might have the videotapes.