I don't think the 5.2 would even need thin head gaskets. Remember, the Magnum engines have a shorter deck height, so they have higher compression already. IMO, if he finds a good low mileage 5.2 (they are still out there) all he needs do is put a chinesium Air Gap, a 650 DP, a good distributor with a hot advance curve and a set of long tube headers and he's so close to 300HP he'd never feel the difference.