Question on the AM P-51C...

Decided to try and build this one instead for my Tuskegee Airman friend-- the detail in side is better and if I am careful I htink I can overcome the fit problems...my attempts at scratch-building for the Tamiya B were embarrassing.

A question though-- I have the bagged version with what I can only imagine is a different version of the instruction sheet. In fact-- this one seems like someone else wrote it and put the AM name on it You don't realize how good those original instructions are until you don't have them. The paint directions are sort of minimal....or at least not up to par with the original kit instructions I think.

Also-- I see lots of extra parts on the kit that aren't at all referenced to in the instructions. I know enough to use the 4 blade prop instead of the extra 3 bladed prop-- but I see two versions of the side panels for the cockpit and am unsure which ones to use?? Also-- there seem to be two versions of the cockpit floor-- one with the wood planking etched in and one without. There are also three different sets of exhaust pipes...

My question is-- how do I know which to use?? Thanks in advance...