Replacing hardwood flooring with plywood

I just bought a house built in the 1920's that has some water damage. All of the hardwood flooring is buckled beyond salvage and is going to have to be stripped down to the original diagonal subfloor. I am just going to use 3/8" BCX to replace the hardwood and cover it with carpet.
The thought of hammering 6,000 typical 1-inch long ringshank underlayment nails to lay around 1200 s.f. of plywood sounds like an awful chore. I don't know of an air nailer that shoots that kind of ammo, but I do have a roofing nailer that shoots 1" roofing nails. That sounds a lot easier... or I could get an air nailer that shoots the 1/4" crown lightweight staples and stitch the plywood down on a 3"x3" grid, which is somewhere around 21,500 staples.
So... are there any other options? Using roofing nails sounds pretty good to me at this point... any opinions?