Advice on camshaft for a 318, please.

Rumblefish360 - Rob
It is a 4 speed and I have an 8 3/4 housing waiting to go in the car. Was thinking of going with 3:23 suregrip. The car has a 7 1/4 presently
That leads me to another question. I am looking for the posi/sure grip third member. What is the difference between the 741, 742 and the 489 case? Is there one I should be looking at in particular?
Greg