340/mag360 exhaust manifolds

Hi sorry to take so long to get back but I was in the shop all day with my son working on his Duster and installing a "go wing" I got him for Christmas, so I will do my best to post some pic's here to show the clearance issue I have, of the three pic's you sent only the top manifold in the top pic could work, you will see the style I have if my pic's turn out, and I can only use center dump, what I meant by large diameter is the largest I can get in that style as currently I have the 1 3/4 on the d/s and 17/8 on the p/s so if I can go bigger thats what I want or if you think there might be room to machine it bigger, thanks again for all the help