Chevrolet: engine id??, cast iron block, gm motor

Question
dear Jim
could you please help us if you would know if the numbers that we supply you are gm or not?? as the people we are buying this motor from do not know if it is a gm motor or a ford they tell us that it is a gen111 (Ls1) but it has a cast iron block and looks like it has OHC we are in australia and a quick response would be much appreciated
the numbers are as following
2U  99227  3032056  5020
these are the only numbers that we have been given
regards daryl

Answer
Daryl,
    Well, the only 303 number I can come up with is 3030817, which was a 73 to 76 GM 400cid motor. I can't find anything; head, intake, exhaust, or crank with that number. I can tell you that it is not a ford stamp though. It has the sound and feel of a GM casting number, but without looking at the block I can't tell if it has been re-stamped; ie. when the block is machined or decked during re-build, they sometimes restamp the block and get it wrong. You can look on the intake for a raised-cast firing order number: number should be 1-8-4-3-6-5-7-2, and tell if it is a GM motor, but if it has an aftermarket intake that's not much help. If the valve cover can be removed and the number gotten off of the head, I could ID it that way, should be near the center of the head on the raised journal. Otherwise the number you were given doesn't come up in anything I have. Sorry I couldn't be of more help... if you can come up with the head or intake number let me know - I'll be checking back off and on all day today.