Hi, I am going to install about 1000 sf of 3/4 inch prefinished flooring myself. I was looking at an air flooring nailer at Harbor Freight that says it is for 1/2" or 25/32" flooring. Most of the spendier ones I saw specifically say they are for 1/2", 5/8", 3/4" and 25/32" flooring. My question is will the cheaper nailer work for my 3/4" flooring if I use the 25/32 inch spacer or do I need one that specifies it is for 3/4"? Thanks

You can use the HF nailer. Just add an additional 1/8" to the 5/8" spacer. Anything that's 1/8"( like a piece of masonite), with some sturdy double face tape.
Do some testing. You will want the staple to seat flush ( slightly countersunk ), right in the crease at the top of the groove. The 25/32 is very close, but may be a little high.

I think Floorologist meant, the crease at the top of the tongue; but otehrwise he is right about the nailer, using some form of shim will allow you to modify the nailer for 3/4 inch floor.