I am sure someone can help you with block numbers, But it sounds like you do not have a super motor. I believe the late model fleet lines started having Tach drive/hour meter plate below distributor.
The biggest oversize bore is a 3.75. If you go any bigger you would need to machine the block for bigger bore. I don't believe there is a off the shelf automotive piston that has correct wrist pin height for stock stroke so if you do not want to stroke it you would need to have a custom piston made or use a tractor piston from a bigger Oliver that may work, that would be from the 88 block family (88/1650) etc.
If rules allow you would be best with replacing the block with a bigger block, 88, 320 block or 310 block.