C6 into a 64 crossmember question?

I have a 390 with a C6 iam putting into my gal. And I was told that when you switch from the cruiso to a c6 you need to modifiy or get a new crossmember. Wich crossmember from crites will work? Or would it be easier to just fab something up on the existing crossmember? Thanks Fred.

i have a c6 in mine and all the was done was some steel plates on each end and the holes were drilled and it fits quite nicely in my 63