need help w/engine casting dates!
 

just got em cleaned off,..........and it looks like the casting date on my 170 ci 6 cylinder motor is .............
c5 de 6015 H ..............
exhaust manifold is c3 de 9430 A
intake maniforld is c5 de 6090 A
the serial number of my car is 5fo8u 135798, is this probably the original motor for my car??
getting ready to start digging in on this pony,........... i tried to find info on line, but couldnt find much. everyone is more knowledgeable about the v8 models!
thanks guys!!