Speed is $...

Both but!!!!!

Realize the cam will add power but the larger the duration the higher the operating rpm will be.

Also, if there is no cylinder head support to not only flow better but to also handle the higher lifts that are normally paired with bigger camshafts, the limited airflow will not allow the power to come flowing through.

I suggest purchasing a cam and cylinder heads to meet your goals. Don’t shoot for a facet HP by rather a time slip on the track even though you may never go. It’s easier for most of us to assemble a package of parts to meet a drag strip ET than anything else. Be prepared for a complete car package.