You absolutely DO NOT want to run both puller and pusher fans on the same radiator! You are simply blocking air flow through the finned tubes with one of them. The key to success is having a properly shrouded fan in place, so that every bit of air pulled or pushed by that fan is going through the fins. For an electric fan the easiest "shroud" is a piece of aluminum sheet that spans the radiator core with the sides folded down and attached to the outer supports, and a hole slightly smaller than your fan OD. The radiator on my '33 came from PRC with a SPAL puller fan mounted to just such a shroud, and I then added a SPAL fan controller for programmable set points.