If you have an 86 up engine, some components do not cross over to the earlier engines. The 86 up engines have a 1 piece rear seal and use a different bolt pattern on the crank shaft. Subsequently the flex plate mounting will be different. Also there are some differences in the cylinder head to intake mounting. It's difficult to say what you have as many engines get mixed and matched. As you stated you don't want to purchase a bunch of stuff that won't interchange.
Fred
