HP numbers from any dyno, chassis or engine is just the first step. I prefer an engine dyno, because you can get more data to decide if it needs tuning, and or what is right or not right with the combo. While nothing stops you from having exhaust gas temps, 02's, fuel flow, BSFC, etc. nobody usually takes the time to set up an engine on a chassis dyno. To tune your combination I would want to know cranking compression, to get a handle on dynamic compression ratio, and exhaust temps, along with 02 readings to see how efficient combustion is. One HP per cubic inch is what I use as a reasonable goal on a mild engine with bolt on's as you describe.