Some of the last LA engines were available with roller lifters and have the bolt holes for the roller lifter holddown. Carbureted LA engines have the mechanical fuel pump bolted to the timing cover. The nose of the cam on these engines are longer to accept the fuel pump eccentric. If you do use an LA cam and proper lifters, you need to check clearance between the cam sprocket bolt and the timing cover. You may have clearance problems. I think you will have less headaches using a cam for the Magnum or have a cam ground from a Magnum core, if you are wanting something that is not available.