I bought a package deal that included a 65 273 that was rebuilt. When I pulled the valve covers I found later style, hydraulic rocker arms. I have not pulled the intake yet to see what lifters are there, but I am thinking about replacing the cam anyways with a aftermarket hydraulic cam, lifters and running the later style arms that are on it now since I don't have the mechanical rockers and pushrods. Any problems putting a hydraulic cam in a early block? It will be a 2bbl motor in a 65 Dart convertable with a auto.