What you would be looking for is a 1966-72 7500-8500 series truck which would be in a conventional cab H or J series, Tilt Cabs L, T and W series. Non Magnum 401s from 1960-65 could be found in 6500 series Trucks such as the Conventional cabs, B series and Tilt L series, still a vast improvement over the 305 and you can always upgrade to the Magnum heads and manifolds. Looks like Ed gave you a lead on a 401, if it's within you're driving range it's worth looking into
