been looking at different bellhousing casting numbers tying to determine which would be best for me... some are listed as for E Body, and some as truck, etc. What's the difference? Does the clutch pedal mechanism bolt up the same?

There is probably a difference between the z bar mounts but also the truck clutch is an 11" and the car clutch is 10 1/2" which may or may not make a difference. I assume your talking small block?
What part numbers are you looking at?