I am looking for an engine to replace the one in my 1989 XJS Convertible (mine overheated and dropped a valve seat).

I know that the HE engines began in 1981 and the '89 had the Marelli ignition. Will the '88 and earlier engines fit into my '89? How about the 1990 engine? If I use an earlier engine do I need to change the ECU?

When looking for a used engine I assume that I can look at the number stamped on the engine to determine its date of manufacture. Where are the numbers located on the engine? What number/digit indicates the year it was made?

Thanks!
Mark