The serial numbers are located on the side of the intake ports. That is 90 degrees from the intake port face where the pipes bolt to the cylinder heads. You may only be able to see one in the front and one in the back of the engine. If they were acquired at the same time as a set or with an engine built by ECi, I may be able to get all 4 of the serial numbers if you give me one of them. The serial numbers are a 4 or 5 digit number followed by a dash and then another number or two.
I have the ECi computer database and that is how I can do the research.
I can be reached at office # 251 436 8122 or email;