dyno
Here is my opinion, and how I see this. If the motor was not dynoed at Naylors and in fact it had some potential problems as stated by the buyer, than reguardless of the dyno number, he did not get what he paid for. If the dyno number is important to the buyer and the motor was advertised as producing the HP number advertised, than the builder should back up that claim.
Do HP numbers vary and can they vary from one dyno to another, yep for sure.
Dynos are used as a tool to help break in motor and dynamically check the engine out. They are also a great tool to baseline and get an understanding of the engine power.
Will it give you an ET, nope, will it give you an idea if you should be faster, possibly !!
That all being said, taking all this info at stated as being correct, I think the buyer is being patient and seems to be adressing this properly.
I do feel that Naylor should try and make a little more effort to help this situation out. Even if its just calling the buyer or posting clear honest info.
As we know bad news travels "faster" than good news.
And I can tell you that with out "dyno Results" :)
Take care JMO