I tried once taking the circuit board out of one of my son's r/c toys and hooking it up to a tank's motor. Couldn't get it to work. He also has a racer car with variable speed and reverse he is willing to sacrifice but before I do it does anyone have any suggestions. i want to put it in a 1/25 panther with dual motors

I'm no expert on this but have a look at www.modeltanks.co.uk . See 'converting to rc' if it's the Academy Panther you have this may help