My understanding of the situation is slightly different.
It's documented that Jimmy Dean was, for a while, one of many stunt testers for Beat The Clock in the early 1950s. It's certainly true that many of the stunts in Beat The Clock were of interest to these parts, normally with wives messing their husbands up, so I would he surprised if Dean didn't take an occasional splosh in the line of duty, behind the scenes. However, it is not proven that he, or any of the stunt testers, actually appeared on the show as televised, so I don't believe footage of Dean in this context survives to this day, and I do not expect this line of enquiry to contribute towards a positive answer to the headline question. (Without ruling it out altogether!)
However, there was an article in Boys Life magazine in 1953 about the testing process with several grainy monochrome photos, at least one of which is about a messy stunt and at least another of which features JD. Sadly these pictures are not one and the same, but hopefully this might guide your imagination.
Not helpful for your question, but this reminded me that James Deen (the straight porn star) gets pied at the start of a scene with Marie McCray called Dirty Games.
I got this on tape years ago. A friend of mine loved this because he loved when guys are pied against their will, and this guy definitely was. They sure got out a lot, as they both named a whole bunch of places they went together.
The 1969 version of BEAT THE CLOCK was taped in Montreal, hence all the places they visited were in Quebec or Upstate NY.