the exhaust valves are too big as standard anyway.
Only the inlets need changing if theres enough casting to support the bigger valves,
U want to ideally use a hemi head as oppose to the lean burn.
So something like an <86 or if your lucky ford used some hemi heads post 86.
Then theres also the efi head which is a hemi but would need an adapter plate. Expect 110-115 at the wheels with like sorted cossie has said. I miss my cvh on a 4-2-1 ashley.

I'll dig a video up