This one. I have the same four core & planned on ordering it this summer. I was going to fashion it as a puller as the snout of the H20 pump fits right between the fans.
I have a 16" on the front of my '73 with a four core Champion. According to what I have gleamed a four core requires a pusher as a puller can't pull the air well enough through the width of the deep fins whereas the pusher reportedly can.