I am starting work on my 390 FE. Bore and stroke confirm it's a 390. Inside the lifter gallery there is "D4TE-1" I take that to be a 1974 truck engine. "OJ5" is located under the fuel pump mounting surface. This is the date code ,correct? There are 2 other markings that I cannot find any info on. On the passenger side, in front of the#1 cylinder is stamped into the block
"F21705". The other is located under the #4 cylinder on the side of the block. It's cast proud and states "SPECIAL". Any clues on these?