First off headgasket? Your kidding me... How much PSI do you plan on running on the JRSC? Stock 6psi smaller pulley 8psi. No headgasket needed for 8psi(but would reccomend Water Injection to control temp)

Recommended order(IMHO)
JRSC & Clutch
Intake & Cam Gears
Exhuast
Headers
Ignition
8psi Pulley and water inj
Fuel stuff...

But ask John at Spec-R he could tell you more.
If you plan on running more than 8psi then you need to lower compression etc...

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RiceRocket & The Blue Bullet Eating Fords and Shitting Chevys