Ok you really need to specify exactly what you are looking for.
best? the only way you can get gt40 heads are on a 93 cobra and an early 96 explorer. the gt40p's are a different type of head that need special exhaust headers.
Hmmm I thought several years of the explorer had those heads? Was there any difference between the cobra and the explorer head ie: port size, combustion chamber cc's?
The 96 Explorer's had the std GT40 heads(like the 93 Cobra 5.0). At some point in 1997, the switch to the GT40P heads was made. These are the ones with the revised spark plug locations and header fitment issues. They also have the same smaller exhaust valves that the std small block Ford heads had (1.45-1.48)