I do plan to write an illustrated guide to Tomcat blocks, but might be a few months. I don't know anywhere that really goes into the blocks, but there is some stuff here:
Tomcat Alley - The F-14 Website Click on each block for some notes. "Real" F-14's start at block 70---everything else is usually one-of-a-kind and test planes, though VF-124 got a few block 65's.
The gun vents are exactly that---vents for the gun. Gun is on the lower left side of the nose. There are several variations to the gun vents---some are block-specific, some are time-specific. All F-14B's and D's always have the same style, the final style. But the A's were built with 1 of 2 styles, neither of which is like the B/D style. But they were all eventually changed to B/D style. The style on VF-84/111 is the 2nd style. The VF-154 has the 3rd, B/D style as those A's had been modified by then.
(gun vents vary on many planes---the F-16A/B have different ones than the C/D, and F-18's have 2 styles as well, which changed early in C/D production---it is very often a key thing to help identify plane variants, as so many things are internal)