Sorry guy, but this is one of the places where you gotta bite the bullet. There really is nothing that fits a 31 Chevy except a 31 Chevy rad or an aftermarket radiator. I have been building hotrods forever, and I know. I refuse to pay the horrendous price charged by the aftermarket in Canada (there is no aftermarket producers in Canada, only stuff imported from USA.), and it ends up costing twice as much as you pay in the states. Generally I take my grill shell down to the radiator shop, and hunt around through all of their "left over" top and bottom tanks untill I find something the correct width and thickness, with a cooling loop for the automatic tranny in the bottom tank, and then get them to put in a new core and move the inlets/outlets around to suit. This still ends up costing me about $400, but if I buy an aftermarket rad it costs me between $500 and $800