If you go to an HEI the late 70's 250 inline 6 cylinder one is almost a straight drop in. Most will actually turn the oil pump but the tang on the distributor shaft is just barely in the groove of the oil pump shaft so some needs to be turned off the hold down shoulder. Speedway makes a hold down clamp just for this application. Early on they used a coil that was remotely mounted but I think all the replacement ones are coil-in-cap. A really good distributor.
