Those look like 6300 series - 600 AX, the first aero brake levers. Shimano releases the 7300 and 6300 "Aerodynamic" components sometime around 1981. They didn't catch on, so they're uncommon. You will have great difficulty finding hoods for those. Sorry.
You could get 6208 non-aero levers, or 6209 Aero levers. Or go with 6400s. You may still have a hood problem, but I think you'd have better luck.
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