I apologize in advance if this question has been approached already..( sure it has, just cant find it).. i have aluminum heads on the sbc, brand unknown as their is literally no stamps, cast #s or the like. The exhaust ports are basically square..1.400 x 1.340 at the very edge of the opening..the headers i have are of course are with round opening in the flanges... I am wondering which gasket would be best to seal and hold up..or, get some rectangular port flanges and swap them out? with that said, the flanges I have found are like 1.625 and larger...any input?..thanks in advance