Small vs big block distributors

This may be a stupid question, but I've asked those before too.

I assume the difference between small block and big block distributors is the deck height (or more precisely, the height from the cam to the intake deck) and as a consequence, the height of the mating flange. Having said this, some of the aftermarket distributors say they can be used for both.

I'm selling a tach drive HEI and a guy with a big block wants it. I don't think it will fit but wanted to be sure.

A Chevy Dizzy fits SBC or BBC. Same dimensions.

That is the nice part about Chevy . As said By Biggy2Birdie they will fit both.

Unless it's a tall deck truck block. But then, GM never made one of those with a tach drive either......

But hey, all they needed to do was lower the dizzy mount pad on the intake. Maybe they did??

Or you mill the collar off the housing and go with an adjustable collar.

Thanks guys. Now I know.