Yes. You will need the valve covers too as they will be 13 hole instead of 11 like your Romeos. You'll also be going to the 4 thread spark plug holes vs the 8 in your 2004 heads. This is fine if your friend actually used a torque wrench and anti seize when he did his plugs.
You also might need new hardware for your timing cover but the cover itself will line right up.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.