welcome. the rear seal changed between the 660 block(older design) of the 599 block(new design, shares with the 6.5) the older block has the 2 piece seal. there are a few differences over the years. do you know what year the engine is?
post questions in the 6.2 sections, it's under the 6.2/6.5 section on the main page. lots of people with all sorts of experience. the only dumb questions are ones you don't ask.