Ceramic Headers 67-69 Barracuda 340

Summit Racings response to why Doug's headers will not work with a 727 transmission: Is most likely because of the bell housing.
So their not 100% sure, anyone with thoughts on this please feel free.
I already have a full brand new 2 1/2" mandrel bend exhaust installed in my car front to back, all I wanted was a pair of really good quailty ceramic headers that would just bolt straight into the existing exhaust like my Hooker competition headers did, it appears with TTI and Doug's this will not be the case.