what are the differences between these 2 trannys?
How can i distinguish between the 2?
Which is better for pulling?

Well the easiest way I use to tell the two apart is the C4 has a removable Bell housing and the C6 doesn't ..
Which is better for pulling .. I'd say the C6 cause I have seen more of them on pulling circuit.. but you can make a C4 hold up to 1000 H.p. and you can do the same with the C6.

If you have either one your in good shape.

The biggest debt that's out there is which one has less power loss to the drive train.. which I hear the C4 has less.

But if your using it with a Stroker 460 you have plenty of power.

ShaZam

it would be worth my time to buy a truck witha C4 or C6 im not sure which yet for 150 dollars and rebuild and put in the pulling truck?

Well if you buy a Truck 95% chance it's got a C6 in it ..the C4's where more of a Car tranny ...