Before building an engine there are a lot of things to consider and usually some kind of budget. Below is a downloadable (excel document) check list covering most of the parts you need to consider when buying or ordering parts. Remember to budget for other things like carburettors, air filter and exhaust system.
A bunch of photos of a complete engine and gearbox rebuild. The gearbox is built into a casing from a ADO16 and has been converted to use on a Mini.
N.B. Video at the end