got told NOT to get a converter.......

Yeah those factory manifolds (especailly if they are A body ones) dont flow well at all.

Another reason you need a converter. With all that duration of the .509" cam and low compression its not going to idle well. A tight converter is going to make things worse. Loosen the converter up will elp and your car wont want to creep at a traffic light with your foot on the brake.