Anybody ever see these marks

[js27]

I just bought a complete 70 F-383 HP and when I gunk down the block I saw these letters. Anybody ever see these before ? Also there are two 3's stamped on the driver side pad--anybody know what these stand for ?
JS27

[6bblgt]

the letters on the side of the block are bore sizes for individual piston selection at original engine assembly

it's a "blueprinting" method for engine mass production to obtain the ideal piston fit,
pistons would've been batched by size also: A, B, C, D, etc.

[Burdar]

Those letters represent how far out of spec the block was machined.  I would imagine most blocks had them.

[HP_Cuda]

Pretty cool, haven't seen those marks before.

[1 Wild R/T]

  Nope.. Never...

[js27]

Wow I would never have guessed that. Learn something new every day. How about the number 3 stamped on the driver side pad ??
JS27