OK ... bear with me as I have more photos of the rear deck to decide which one I use. I promise these are the last but I combined them for better angles easier comparison.
In both images the original Tamiya engine lid is on the left and the Revell 1/25 lid is on the right.
You can see the bulge created for the '68 model year in the side shots. This is very noticeable with both side by side. The 3/4 view also amplifies the different shape.
I'm pretty well convinced the newer, though smaller, Revell hood should be used. I'll have to sand and smooth the lip on the body for a smoother transition.