I expect you're looking for a short one to fit in a Camaro/Chevelle?.
As an aside to the subject, anyone else ever seen a short 400 w/ the GM unifit bolt pattern bellhousing before?.
I saw one only ever, loose in a pile at a boneyard...should've grabbed it but didn't..
Came across lots of Turbo 350's w/ the unifit pattern over the years but only the one 400..
~ Pete