The 2.8, 3.1, and 3.4 are all what's known as Even-Fire engines, meaning that they are sequential, 1 thru 6. There was an early version of the 2.8 that was an Odd-Fire engine, according to my brother-in-law. That firing order was 1, 2, 3, 4, 6, 5. Supposedly it was bad about breaking crankshafts, being the reason for the development of the Even-Fire crank.
Those 1, 3, and 5 cylinder wires really had a hard bend in them, the way they were routed.