Using a Floor Jack as a Transmission Jack?

another time using a floor jack doing a trans in a Dakota. My son was under truck helping me. This time jack slid out sideways, pinched my son's thumb and broke it just below the nail, he wound up having to have surgery to fix thumb.... I now have an old Lincoln trans jack for doing them off the floor and a (I'm embarassed to say this part) for now an HF trans jack for use under my 2 post lift that I didnt have back then...... looking for an old school Lincoln, Blackhawk, etc trans jack so I can rid myself of the HF one