I have a 65 with a 289 but when I bought it, the owner told me it had a different cam. I'm pretty sure it was running on the 15426378. It ran pretty well for months then all of a sudden started running rough. The timing chain was a little loose so it was changed but now I can only get it to run on the 13726548 after trying with the old firing order but I can tell its not right. My question is if the timing is set correctly and I switch the wires to the other firing order, shouldn't the car keep that timing but just change the firing order?