G'day! My radiator on the '33 is tilted back right at 20degrees. Because of the clearance with the engine I'm running an electric puller fan on the back side, but would rather it be a straight mechanical drive fan. The biggest thing I see there would be that the fan shroud is going to need to be made to extend back for proper flow. With a custom shroud there's no problem with tilting - just look at the Shelby Cobra for an example.
You want the lower radiator outlet to be on the same side of the engine as the water pump inlet, as much for ease of routing as anything, and be sure that your lower hose has an internal spring to prevent it sucking shut at high flow.
Easiest way to determine your radiator need is to look at the OEM radiator for the donor vehicle for area and number of row reference as a starting point, and don't go smaller, IMO.