Stock headlights in '71 were either used 6012 or 6014 lamps.
6012s are nominall 50/40 Watts
6014s are nominally 60/50 Watts.
H6024 are generally 65/35 Watts but the GE H6024NH are 65/55 Watts
H4/HB2 type bulbs (used in seperate lamp housing) are nominally 60/55 Watts
http://www.candlepowerforums.com/vb/showthread.php?392498-Interesting-headlight-bulb-test-results
My understanding is the nominal power draws are at 12.8 Volts (US standard)
At high voltage, lets say system is regulated to 14.2 Volts, bulb power draw will be higher than the nominals

If you want to ballpark worst case:
Say 75 Watts at 14 Volts = 5.35 amps for each lamp, or roughly 11 amps for the pair.
Circuit breaker in the A bodies was 15 amps.