With the eheads I dont see why it wouldnt be capable of 550hp with ti retainers if you were willing to spin it up and tollerate the manners. May even hook better. I agree it would need more gear and convertor compared to the 455 counter part. And hydroboost the powers brakes.
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'78 Macho T/A DKM#95, 460cid, SRP pistons, KRE 310 D ports,
3" pypes, Hooker 1 3/4" headers, hydraulic roller,
10" Continental, 3.42 gears
11.5 @117.5mph 3900lbs 
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