I have a 65 Coronet 500, I am planning on swaping the K frame out in favor of a 70-72 B body unit. I have seen this done but I did not get a look at the transmission crossmember. Do I have to use a different one? Is the steering column still going to work? What about the torsion bars? I know this will move the motor/trans back, that is why I am asking.

I did it to the hot rod. You will have to modify the transmission crossmember a wee bit. I turned mine around backward for the 4 speed I dropped in. With the 727 I stuck the tranny mount in the center of the crossmember.
You will need to shorten the drive shaft.

If you have a column shift automatic the exhaust manifold will not fit around the shift brackets on the column under the hood. The column length will be the same.

If using a 4 speed the pivot mount on the frame rail will need to be moved and the linkage modified.