Is there a serial number on the engine, and heads that has the build dates? I have an 86' GT, but I suspect a later model engine may be in my car. I already know the tranny is a 90-93 model AOD. I suspect maybe the previous owners found a wrecked donar car and swaped the drivetrain out. I am hoping they did, because I want to get a set of aftermarket heads, but an 86' engine with flat top pistons complicates matters. How do I tell? I noticed that the oil pan has two drain plugs, I thought only later model 5.0s had this.