Paul, When I was looking for a new side oiler block for my galaxie, I was told to look for blocks with the following casting no's, C4AE, C5AE-A,C6AE-B etc. They also told me to stay away from the following casting no's C6JE-B (MARINE APPLICATION) and C5JE-D (IRRIGATION APPLICATION) I was told the blocks that were used in marine and irrigation applications weren't the same quality as the high performence car motors. I know marine/irrigation motors didn't use dome pistons or forged cranks and pistons but, what was the diff in the blocks? I paid $2500 for a block only that needed to be machined (C5AE-D) Here's my problem, when I was buying this block, John Veermesch of Total Performence in MT.Clemmens MI. (Huge Ford Guru!) Had 2 Marine blocks in good condition and he would sell them to me for a couple hundred bucks ea. He said I would be nuts to put them in a car pushing over 500hp (C6JE-B). He say's the castings had small flaws and some other minor imperfections that didn't meet fords QC for the High performence motors. Your in-put?