TRexGAWD

I'm going to laugh if OP has a SBC under the hood.. All you'd have to really do is get us the PN of the plugs you're using now or the ones you had..

djd2392

okay..ill snag some pics in the engine bay

djd2392

for the record, im new to the 5.0 world hahaha

djd2392

Looks like a normal 5.0 to me... unless i;m crazy, let me see if i can grab that part number too

javila2468

Cant tell whats heads those are...look like stockers but could be wrong...take off the driver side valve cover and snap a clear picture of that

djd2392

If i can find time i will haha

CW

Was anymore info found on this?
I sold a 5.0L with a stang and the guy is telling me now 3 years later that his mechanic says I sold him a triton truck motor all based on them not able to find plugs to fit.
Same thing everything is normal 5.0 except the plug holes.

Mike T

I don't guess he could find the time.

rmodel65

maybe its an old motor...some of the older heads used a larger spark plug

CW

Upon further research I also found that the GT40 and GT40P heads use a different plug with longer threads, almost twice as long as other 5.0 heads such as the E7's.
Search up how to identify GT40 heads and you will find easily seen markings and casting # listings. The three verticle bars on the end of the heads is a sign of GT40 and 4 bars is gt40p. Read this, there is links to pics of what I mean that may help you.
http://www.fiveohinfo.com/performance/gt40-gt40p.html