matching numbers

I have a 74 MGB and I want to make sure it has the original engine in it. Can someone tell me how to check the numbers on that subject?

There is no way to check numbers for proof of original engine. You can get a Heritage Certificate that should tell you what the original engine serial number was. Does your engine have the aluminum engine number plate on the block between cylinders 2 and 3? If it is there it should read 18V-672-Z-L Engine# between 101-38093. That would indicate it is a non overdrive engine for the North American market for car serial # 294251-360069. Dates covered are Aug 72 to Sep 74. Overdrive cars are 18V-673-Z-L with other number similar to the above. If you don't have the engine plate, they get eaten up if the engine has been rebuilt andhot tanked without removing the plate. Your engine could also have been changed at some point with another engine from the same year and have the right plate but would not be the original engine. If you don't have the engine plate it would be difficult to impossible to be sure if you have the OE engine. It isn't as important to know this information on an MGB as it is on some high dollar USA cars where there were several engine and option choices. I know I didn't answer your question and other than getting a heritage Certificate I doubt anyone can tell you for sure.
Clifton Gordon