I don't know about the "worst" beater, but I had the "best" beater ;) Wish I still had it.
1961 Willys Pickup. It used to be a fire truck for the Big Moose fire department so it was painted fire engine red (not well either) and had emergency vehicle lighting up top. There was a water tank in the bed, but they removed that when I purchased.
That truck was my favorite even though it could barely go 55 mph. I had a flathed line 6 in it with the original "army" type wheels and tires. The bed was pretty rotten in spots although it could have been repaired. The cab was in great shape.
I left it with someone when I moved because I didn't trust it to make the long journey and had no where to store it, and eventually it stopped running and parts started missing.
If I still had it, it would have been cool to use it a mtb shuttle vehicle or something dumb like that.
The only pictures I had were on film, and I don't even know if I could find one, but it looked something like this (it used to be painted teal like that and I had always wanted to restore it to the original color):