Did you by chance get the single point four leg lifting sling with it? There should be four lifting pads on it, two about a third of the way back from the bow and the other two just ahead of the engine compartment. If not, a crane company can lift it with a 100 to 150 ton hydraulic truck crane, (its 150 ton ONLY ten feet off the pin, any farther out, like centering on the well deck and the capacity of the crane drops off QUICKLY ) The crane company should also be able to provide a four leg lifting bridle and shackles capable of the tonnage needed. They make some nice kevlar lift straps now that wouldn't notice 28 tons.
The LCM-6 will be easier to lift that our Mike-8 boats, that boat (if unmodified) has a lifting weight of 28 tons (actually officially listed as 56,000 Lbs in the Navtra small craft manual. Its going to take a serious permit to move it its 56 ft long and 14 ft wide. so that is gonna be more an issue than the weight. (many states allow 40 tons on the road with a seven axle 'stinger' rig under them.)
Is it afloat, and can it be towed to a haul-out yard? THAT might be easier, (unless its sitting dry stored in a surplus yard. Then its hauling only usually. Nice thing is that after the repair yard is done, any yard with even the smaller 35 ton standard Marine Travelift will easily handle the boat. As you can see from the last two pictures here, that Military Issue four leg bridle has a CERTAIN amount of difficulty in working with them. Our Sea Cadets thought it "FUN", being somewhat older, my crews don't share that thought. Lol.
The engines are usually Detroit 6-71 diesels with Paragon gears unless refitted with the Twin Disc's. If they're not damaged, they're both good gears. There's a surplus dealer over in South Chicago, Adleman's and he's just gotten in some NICE Detroit 8-92's that would bolt right up in there. They advertize on several military vehicle sites as well as Facebook Marketplace. our outfit, Firelands Military Vehicle Group has bought from them, Nice folks and easy to deal with.
Wish we were closer to you, we'd have been able to help some anyway. But good luck