Check on the 440 source website under starters. I think they talk about the various sizes there. If your looking for info on correct date coded things, you might want to post in the Restoration & A12 section. Those guys know their parts and numbers.

I just noticed you sig. Did you see my post about the 1970 RT Challenger survivor this guy at my work bought new in '70. I just learned about it last week, and am waiting to get over and take pictures of it. It's all original, never apart, and is a little rough according to him. You guys need to talk.

1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)