Re: HP Cleveland build up
My cam is Ford Motorsport, same lift as you but just a tad less on the duration you quoted. But me reckons the duration figures you quoted not for 1.73 rocker ratio, because I'm sure my cam grind is the biggest solid Ford Motorsport pruduce.
Either way agree with russ don't waste your time on a vac secondary, 750DP bare minium, 800DP better or even 850DP if the Offie manifold is a high rise type ie funnelweb style.
Also agree 10.5:1 not enough to make best use of those heads and cam, sure it will run on premium unleaded but expect a motor with a lazy/soggy bottom end response at 10.5:1.