M code and H code engines for about the first half of the 1970 production year were 351W, not 351C. The Clevelands started showing up in either December 1969 or January 1970. I know guys who were waiting to order Mustangs until they were available.
The earliest casting dates on Cleveland parts is about August 1969 (there are some late July heads) and it takes 3 months between the time the parts are cast and when the engines assembled from those castings arrive in showrooms.
John the streetable cams, with early opening exhaust valves (to contend with cast iron manifolds and mufflers), relatively late opening intake valves, and low overlap can contend with a wide range of engines. I can spec other grinds with less overlap than the proposed Cobra Jet cam in this thread.
If you haven't purchased pistons yet, you may want to consider the Sealed Power or Ross pistons with pop-up domes as they get you closer to 10:1 static compression and open up a wider variety of more "streetable" camshaft grinds to choose from (less overlap, later opening intake valve).
Things to ponder.