some place on there you will want some steel for heating , welding , banging and clanging
If you can locate a quarry or concrete plant locally the rubber conveyer belt makes a supper top. Easy to clean. Won't damage anything you throw on it.
I have to agree with this method of building a tough work surface. I built one just like it in 1978 and still using it. It has been in 3 garages and we are still doing heads and transmissions on it today. No dents and it wipes up clean enough for our various garage parties.When I built my bench, I used 2 X 12s for the top. Then covered it with 3/4" plywood. I then took the measurement to my local heating and AC shop and had them make me a top cover using 14 gauge galvanized metal. I had them bend a 1" lip on the front and both ends for added protection for the top. It has been on there for over 20 years and still looks good when ever I clean it off enough to see it.
How about an "out of the box" thought....... one of those commercial bathroom stall dividers. Told ya out of the box. I found it ideal, it's 1 inch thick solid, and stands up to every chemical I've sprayed or spilled on it. It's also a light gray color- good for locating small parts , etc. rebuilt my 833 on it also. Cleans up well too.