340 found numbers here

Answered you already but....

O = 1970
B = Car built at Hamtramck factory (70 Swingers were built at Windsor Canada factory. So engine likely from a duster, maybe E or B body?
235705 = last 6 of cars VIN. 135704th car build at hamtramck factory that model year.

F = 1970 Model year engine
W = "engine" assembled at Windsor factory
340 = self explanatory.
P = premium fuel (high compression engine)
3069 = Day 3069 is Monday, December 22, 1969
0080 = 80th engine assembled at Windsor that day

7/8/69 = day engine block was forged
2780930 = engine casting number (340)
-3 = engine casting revision number (number of times a change was made to the casting molds) Some claim lower better, I don't think it makes any difference. The change may have been made for wear and tear or a flaw in previous. I have seen small blocks go to around 9, but 14 for big blocks.

Maltese cross = 001 undersize bearing. L3 Left bank 3rd rod had undersize bearing (this is my understanding of the symbols). measurement can verify. most of us will take them to .010 x .010 anyway.