Is the expected hp on an early 1970 440 punched 30 over with a mild cam gear drive 4 barrel aluminum intake roughly stock compression 300 hp?

No, the expected horsepower for an early 1970's 440 punched 30 over with a mild cam, gear drive, 4 barrel aluminum intake, and roughly stock compression is not 300 hp. The expected horsepower would be significantly higher than that.

A 440 punched 30 over typically increases the displacement to around 452 cubic inches. With a mild cam, gear drive, 4 barrel aluminum intake, and roughly stock compression, you can expect to see somewhere in the range of 400-450 horsepower. Some high performance setups may even exceed 500 horsepower.