Hi mtnance.
Presumably you have the Moss catalogue handy....
In the front, on P4 & 5 of the regular catalogue section, just after all the fancy shiny stuff that you don't need yet, but crave madly, is information on production years, numbers, engine codes etc. Bless Moss for adding this as it's really useful for some preliminary detective work.
The engine ahould have a number plate on the left side (as you face it from the front of the car). If you remove the rocker cover, you can also check the casting number on the head, and see if this matches the block. For help here try http://www.flowspeed.com/cylinder-ident.htm
Also check out sites like MG esperience http://www.mgexperience.net/ as they also have information.
I hope that is useful,
Ed
I want my MGB