360 running hot…very hot

It's likely a dual pass radiator like 92b said above. The OP made it sound like he bought it new, so he can verify. If it's not a dual pass, that'd be an awfully bad f-up for a 'new' radiator.
True- but since the brand/origin is unknown, I would assume nothing, especially with the proliferation of cheap offshore radiators. It's easy enough to verify- just snake a piece of wire/coathanger/welding rod straight down the inside of the tank from the top radiator inlet and see if you hit a baffle.