Hey, Charlie! I also have one of the original Eisbrenner fiberglass "bucks" - as I recall the story, he fabbed up 8 or 10 of the windowless, featureless fiberglass bodies then built one -- the one that was featured in Scale Auto Enthusiast (Issue 21, Sept/Oct 1982).
I also scored two of the Uptown Auto resin castings - one is a work in progress.
I love the Seagrave Anniversary Series trucks - especially the Sedan Pumpers - which the Eisbrenner fiberglass units and the subsequent Uptown resin castings represent.
If you have pics of the two you've built, I for one would love to see them!