That cam is not suited for Cleveland 4-V heads. Not nearly enough duration to make it "work". The car will run MUCH better across the range with 2-V heads (that cam). Are they '70 ("quench") or '71-newer heads?
4-V heads are not really the hot lick for a street engine. We get much more "usable" power (in the operating range of a street engine) with 2-V heads, with large valves installed. No porting necessary, just a little "blending".
The strong point of the Cleveland 4-V is it's ability to rev. With only 218 @ .050" lift, RPM can't approach the sweet spot. BTW, it's better to list the "@.050" duration for a semi-accurate comparison to other cams.
Cleveland heads, not unlike BBC heads, "like" more lift than the average. With the 4-V heads, you should have a minimum of 230 @ .050" and .550" lift, to make the heads "work". You should also have at least 6 degrees more duration on the exhaust side. Clevelands are exhaust-impaired.
An open-plenum works very well for high-rev engines. For that cam, I agree, a dual plane (like Performer) is the better choice, but again, we're back to "which heads?".
IMO, Cleveland is far and away the best small block Ford for high-end performance. Apparently Robert Yates agrees... Built correctly, Cleveland is a GREAT engine.