I would just look up on facebook marketplace gt40P or look up an explorer motor and strip the motor, then have them rebuilt. I am still seeing the explorer motors compete with serpentine system for 500$ in some areas.
Honestly, they are OK heads but I would go aftermarket if I could afford them.
I bought a set of the gt40 from a buddy and had them rebuilt with better components, but in the end I will probably want better heads at some point? maybe...