[DanEC]

I'm assuming they use a dyno to verify their horsepower claims. Part of the answer to your question will depend on what head they use on their 460 HP package stock. If it's a stock police interceptor or plain stock 428 head then I would believe that even a stock set of Edelbrock heads would add some HP. If the stock head is a Cobra Jet head and has been re-worked at all, then their may be some difference, but not a lot. They should be able to bump the compression up a little with an aluminum head, but only a talk with Southern Automotive can see if they take advantage of that.

For what it's worth - my Keith Craft 428 uses a set of 1961 steel 390 high performance heads (401 HP version) that Keith ported, polished, and fitted with larger valves - pretty much re-worked 427 LR heads now. When it was on the dyno I discussed with the operator what he thought the HP increase could be if I installed a set of Edelbrock heads (we didn't get into details on which version or re-worked or not). He said from his experience, it probably would pick up about 35 HP typically.