I have a lowly Harbor Fright 1/2" 120 VAC impact wrench and it'll do it. Paid $40. Extensions and connections reduce torque so when I say it'll do it, I mean with a 7/8" deep impact 1/2" drive socket. The right size on both ends with no extensions or adapters.
Home Depot has a RIGID 1/2" LiOn impact on sale at $150 that has a very good torque rating. Right now it's less expensive than their Ryobi with less torque. Lowes has a promising 1/2" LiOn impact.
Things I've learned, that could be useful here:
LiOn Impact doesn't work well with 2.0 aH battery, needs the 4.0 version. The RIGID ships with a 4.0 battery.
Impact Sockets MUST BE BLACK!!! And it's not the strength, although the black ones are more massive therefore a little stronger. It's the FINISH. A Black socket simply cracks. A Chrome socket can send sharp slivers of chrome at you.