Not all inline-6's have 7 mains. I suppose any of the later ones do, partly explaining the performance from many of them now. But "back then" most only had 5 mains. That was why the old Rambler 6's could out perform alot of other makes, they did have 7 mains. (Anybody older than me remember the Hudson's? 305 CID I think they were, with dual carbs that outran almost anything else for several years in the early 50's.)
Of course I'm comparing apples and oranges here. I'm sure mosty of you are referring to anything but american inline 6's of the 50's and 60's. But that's what I grew up with, and learned to rebuild engines on.
Oh, BTW, I did bend a crank on my '54 Ford pickup with a 223 straight 6 back in the mid-70's. You couldn't see it with your eye, but when I took it in to have it reground, they called back and told me I needed a new one. They couldn't do anything with the one I had. Both bent AND twisted. Trying to do too many stop light drags with the poor old thing
