Also, you need to factor in efficiency of the PSU. if it's rated/tested at 90% efficient, then your 71a can only sustain 62.9a under full load.
Um, what? The efficiency relates to the conversion of alternating current to direct current + waste heat. If a power supply is rated for 1200 watts, 87% efficiency @ 100% load (80plus gold), then it will pull in 1379 watts at the wall, and output 1200 watts DC and 179 watts worth of waste heat. The efficiency has -nothing- to do with the rated DC output amperage. If it says 71 amps @ 12v on the label, it will do 71 amps @ 12v.