Installing 455 in my 67 Olds. Bought a set of stainless headers off ebay and tried putting them in right after I got motor bolted in (2261mounts, engine sits in there beautifully). Driver side header is big problem. While it slides up in there easily, and does lug onto the first (forward) header bolt, flange isnt flush with head as bottom of header is swung too far outboard. If I pull it in to close flushness gap, it hits motor mount and crossmember. What headers do I buy for this combo?