Tell you guys what... (tongue firmly in cheek)
Try scratchbuilding 20 Mk2 40mm mounts (quad 40) in 1/350 for a Tamiya Missouri...then you'll understand why we don't scratchbuild each one!!
I'd be in the mental ward if I had to scratchbuild each of the AA guns for my ships, which I usually replace anyway.
Regards,
Jeff Herne
Modelwarships.com
PS: I just ventured over from the ship forum...how's the service is this bar? :-)