Dougs headers or TTI step headers?

was helping a friend install his 408 indy stroker and tti 13/4 step headers in his 73 challenger and found out they had sent him a-body headers. good thing we looked at the p/n and double checked there web sight before damaging them when installing. one thing that caught my eye was the flange ports in the headers are round and the mopar aluminum heads are more rectangle.although the head ports are easily covered by the exhaust header round tubes just had to call tti and they assured us thats how they are made. something to do with them being the same as w2 heads