Danny, an interesting modellers' site here spells out a difference between the A-31 and A-35 as being an additional intake, offset to port, beneath the cowling of the latter. This appears to be the case of the Grottaglie VV, so perhaps it is a Mk4 after all? Also the radio mast half way back along the upper fuselage appears there too. The model photo below shows an
excrescence on the port fuselage to beat any! Looking rather like a clockwork key it is presumably the propeller/rotor for the target winch mechanism. In at least one of the linked pics the "trailing aerial" fairlead is present. It looks as if you are right and I wrong, and it is indeed for the target wire and not a trailing aerial. A pity that Mr Lax didn't shoot it in colour, as the underside may well be yellow rather than duck egg blue. :-
1/72 Frog and Special Hobby Vultee Vengeance by Carmel J Attard
