I remembered, last night, that I have a brochure on the industrial engines and answered one of my questions with it. The C4PB-6003-C is apparently the part number and the C4PB, is the model number, according to the brochure. I still don't know what the S02690E means, on the model line of the tag.
This brochure is dated 12/68 and the pictured engine, has pent roof VC's, mine has domed Powered By Ford, VC's, so it should be closer to '64. When did the first pent roof's appear? I'll take some picture of the engine today. It's still on the trailer and I need to get the trans, FW and bellhousing off, to check the back of the block, before getting it on a stand.
I tested only one pair of cylinder cores (7-8) but, will check all of them once I get it on a stand. I check, with T-handle, allen wrenches, they give a much better feel, than drill bits. On this check, a 3/16 wrench, would go threw the walls and it was not loose, it would stay and hold. My 5mm wrench (.197), would not enter, at any point.
Fords, original thickness spec for the FE car, cylinder wall, is .170 and the max overbore call out is .060, leaving .140 wall. I can only assume, that it left some tolerance for core shift although, I couldn't find that info.
My plan, at this time, is to have a bore, between 4.125 & 4.130. I'm not shooting for a 460 but, will offset grind this crank, to 3.73 (BBC) or 3.83 stroke, with a SBC journal. I have a source of 6.560 long SBC rods. So, I'm shooting for a 399 - 410 ci engine.