Funny thing about Japan is, every powerful car has 276 hp. What a scam that is.
And in the case of some American muscle cars of the 60's and early 70s', the advertised output was often just a flat out lie to help keep insurance costs down. 410 advertised hp. could be more like 460. as in the case of a Pontiac 455 Super Duty V8, or the famous Hemi, 425 hp. could be like 500.
And as GIR pointed out, whether an engine is properly broken in or not would be a factor.