The problem I see is that the early (92/early 93) mag manis are ~2&5/16 outlets and are very nice pieces whereas the later ones are 1&7/8 which is the dia of one header pri tube on my last BB. yes they would fit (that is important!) and would be fine for a DD 318. the very best manifold combo is a 68-70 340 HP pass iron manifold and an early mag dr side manifold (what I have on the stock car).