Running without a thermostat ok?

Yeah I think that is actually correct about the lower pressure cap. Less stress on hoses and such. Less chance for leaks. Keep in mind a brass/copper radiator the same size and core thickness cools more efficiently than aluminum. Aluminum is cheaper to make and does not corrode as badly. Price a brass/copper VS aluminum about the same size. You'll see. We sold a brass/copper radiator the other day for a Ford LN9000 dump truck. Over 900 bucks. Took three people to bring it in the building. I got very lucky with RobKat. It had a full size three row original copper/brass radiator that the local radiator shop was able to get flowing 100%. It would probably cool a big block Ford in that little car, much less a 302. If everything else in your cooling system fits the bill, the 7 pound cap should work great.