I found a pretty cool solution for mounting a Hi-Lift jack to an ARB bumper using a pair of Chauvet clamps. They’re rated to support a load of 660 lbs each. Best of all they’re about half as expensive as any other solution I’ve found.
For each bracket I cut a 1-1/2″ piece of galvanized pipe as a spacer and used a couple of washers and a nut to hold the Hi-Lift down. I just keep the appropriate box wrench in my glove compartment to remove the jack. I put of piece of bicycle inner tube in each clamp to protect the finish on the bumper. The dust cover is made out of an old wetsuit sleeve. The last tip, which I learned from Greg on our Twain Trip, is to connect the foot of the jack to the lifting tongue with a bungie cord to keep it from rattling.
I’ve used this system for a couple of years now and it works great. Maybe add lock washers to the clamp and mounting bolts if you drive a lot of washboard to keep things from rattling loose.
Here’s a link to the clamps on Amazon: