The big three are probably head flow, cam and displacement. Take 67 273 and 318 there both identical to each other besides bore size (displacement). Cam and head flow is the same. Both engines will flow the same amount of air over time. The 273 is 86% the size of the 318 but the 318 would need about 86% of the rpm to displace the same amount of air through the engine (cfm). Now if you put more cam in the 318 so both would have similar air flow over time per cid ratio the both should have similar powerband. But also if the 318 had the same head flow to cid ratio as the 273 but same cam than both should have the similar powerband. Obviously there other factors but I think there the main 3.
