what the heck is the difference between the 3.0 coupler and the 4.3 or 5.7?

[stang32]

they all have the same splines and the shafts all go into one another. what am i missing?
my reason for asking is, i have a 3.o that needs a new coupler and , i of course have a coupler from a 5.7
3.0 pt # 3854032
and the 5.7 is 3853917

 

[Scott Danforth]

The 3.0 coupler has a wee bit of rubber and beer can thin drive plate

The 5.7 has more rubber and a thicker drive plate

Big block couplings have even thicker drive plates and more bolts

And diesels are thicker yet