[midniteblues]

The the hole in the bell where the bearing retainer seats can be different sizes on the bigger bells.

I haven't seen any of the smaller bells with the bigger hole. I'm not sure if any were made that way.

I think the two sized holes are 4 7/8"(most car trans)
and 5 1/8".(most truck trans).

So it's fairly hard too eyeball the difference between the two with out a tape measure or the two bells side by side.

They do make adapter rings for the bigger holes.
I've also swapped bearing retainers in the past to get the correct size fit of the trans in the bell.

Then finding a Good fitting shifter handle in the truck with a bench can be fun.

And if your gonna use headers finding a set that doesn't hang super low and works with the z bar/bell crank.