Junior, do you have a compressor on-site? In the past, when I lost the bead or had flat, I had 20 minutes downtime max. The worst was when I lost the bead way down in an arroyo (ditch) and had to climb back out and walk the machine back to my truck. What I like about the Galaxy tires (hulk) is that they have a very stiff sidewall and even with a flat you can run it for a short distance.
If you are completely flat and can't get bead (I don't do the ether igniting) wrap a binder strap around the tire, tighten, and air up. You can even put a little grease around the rim to help it seat and keep air in for initial inflation.
The hulk tires are pigs in mud.. no fun but they are great on rock, concrete, nails, and other things because they have such thick rubber pads. There are also, I believe, Galaxy kong's that have less void and more rubber but they would be awful in wet conditions.
As KSSS said, there are other brands. I think Michelin has a galaxy knock off and I know Bobcat does and I like Bobcat's tread pattern better.
One last thing, I bought a heavy duty tire plug kit. I think it's called "blackjack". I've run over a couple of things like rebar or God know's what and the hole was large. Two or three of the plugs sealed it and no problems for a couple of years.
Solid fill means no flats but you lose shock absorbtion, add weight, lose traction, and when the tires wear down, you chunk them and possibly the rim if they can't cut them off clean. Again, your down time due to flat should be 10-20 minutes max.. even if you have three flats you lose an hour. But take the time to use the slime if you do go with air tires... I think the Bobcat Severe Duty would work great on your 773 and give you a little more stability when lifting heavy loads. The 773 can lift more than it's rated for but with standard tires they squat more.
"You Can All Go to Hell, I'm Going to Texas." --Davy Crockett