I may be addicted

More onfo on the Barracuda - the engine number is 4006730-318-18 and on the other side where VIN # should be on block is the number 5R118762 . The rear end is not a 8 3/4 either , it has a rear cover with 9 bolts ( will have pix tomorrow ) . any idea's ? I am a little bummed its not a 340 but oh well , I assumed it was a 318 when i bought it .