I have a 68 C10 with a SBC engine that has the symbol of 5.0L right behind the driver side head. Any other SBC engine that I remember has its Casting Numbers there. So whats up with this 5.0L? Is it a 305 or a 307? Is its casting numbers somewhere else or not at all anywhere? The suffix code doesn't help me at all I find it shows the engine to be a *big block* "AKA", I definitely do know the difference in the two engines. here is some pic's. The last three are I guess sending units, the two above oil filter with a sending unit must be used on computer controlled system being it has more then one wire for hookup ( multi pin socket plug in) this one must be for oil being where it is, other one pass side of block might be a water sending unit ?

Any help would be appreciated, thanks Marvin