That's terrible, JH. Did look like a Manchester cutoff tool tho.
Traditional way is just to rough the lobes in the same cam grinder that you finish in, from the round. Takes a while but they use really hard wheels and push hard. Know a cam shop who finally converted a tracer mill with a hydraulic motor and reduction box to rough mill the lobes, saved them countless hours.
When you said Bonneville I thought it was going to be big - the lobes on large diesels are interesting. They make them separate from the shaft, then expand the bores hydraulically and slide them into position. Release the pressure and clampo ... just the interference fit is enough to keep the lobes in place, no keys or anything. Shows how much torque a shrink fit can withstand.