You will note when buying our early Bronco headers that they list they are not compatible with GT40P heads but they will work with GT40 heads.  Great to know, right?  Just one problem, what if you don’t know which type of heads you have?  This article is written to shed some light on the difference between GT40 and GT40P heads.

GT40 & GT40P heads are a common upgrade for the factory 302 found in the early Bronco.  They are popular because while they are relatively inexpensive they also offer a measurable increase in power to your engine.

To tell the difference, take a look at the castings on the heads themselves.  A GT40 head will have 3 vertical bars on the front of the head with a “GT” cast into the head just below the #1 exhaust.  For GT40P heads, you will find 4 vertical bars on the front of the head and it will be cast with a “GTP” just below the #1 exhaust.