ex header help needed

i have a 1975 dart with 318 engine. recently purchased summit headers, part stated without air pump i pulled the manifolds and i have no air pump but injection heads ( not a small hole but a square hole below ex port) headers flange does not cover completely so small leak does anyone know of a set of headers that will work or of a posible spacer flange that may cover this hole it is square so i can not tap or plug it thanks for reading and any help would be appreciated First time on sight thanks