Valve body knowledge needed.

[jeepthrills01]

So can someone educate me on the difference between these two? Yes the six bolt has part-throttle kickdown...and the four bolt doesn't...but how about what else might be different?

 

[dvw]

Enough not to mix and match parts.
Doug

 

[jeepthrills01]

I picked up the 4 screw as a core..mainly for screws etc...but I didn't notice the difference till I put it next to the other one