Joe, I bought a pile of SBD parts for these kits. I have the two fuselage sprues, I believe the SBD-3 should be marked 3411-0602 and the SBD-4 is 3412-0600. What have you got? I've always heard there was a fit problem in the top front but I haven't built one yet.
It may be that my SBD-3 kit has the same issue because I can't see any difference in the forward fuselage parts between the -3 and the -4. Should there be a fuselage length difference? I wouldn't think so.