I measured all the angles in front of the radiator, and Ive got the same problem as fairlane. Too many obstacles concerning the grill assembly. I can remove most of these if I go to hoodpins, but after thinking thru the rest of the install I found a few other problems. I may have to install a pusher fan to fit the 250 behind the radiator. Won't know until it's in there. Regardless it means butchering the radiator support, which doesn't bother me that much. Relocate the battery to the trunk to allow for plumbing.
I looked at the area below the front cross member and it just looks dangerous. All it would take is one squirrel and poof.
As far as these ebay universal units, you can tell they are imports. Do you suppose they are junk? One of the units I felt I could make work was $130 buy it now. That seems pretty cheap.
Getting creative with mounting for an air-to-air, the trick is to have air flow, so it limits alternatives to front mounting. I have a '67 Shelby hood with about 20 sq. in. of opening. I don't think there is any way I could engine bay mount anything that would work with that.
I wish I had your fab skills Fairlane! Just fit it around everything that's in the way and move on!