I believe the photo I posted was 'J1', cannot confirm that though, I think you will find that most if not all were built with the 'rounded' sills-sponsons and then the 'squared off' panels fitted at a later date, by looking at the front/rear faces of those with 'square layout' you can see the dual panel/rivet layout.
If you look at the pics in post #9 of Micks it shows the 180°c crossover exhaust, most if not all MKIV's used this system, in the first pic of post #10, this is the J1 non crossover setup, it also used a 8 individual stack setup at one stage, the J1 replica-#10- has the rounded sill/sponsons, others are squared off.