Hi, i have a ffr 109 and have looked into this, the short answer is visit EMLRA they have a lot of people with mod specific knowledge.
Long answer is that it can be done.
IF you still have a H/D chassis then it will have 2 settings on the the front dumb irons and on the rear crossmembers, dont know where the term "military shackles" come from as on the HD chassis they are incorporated into the chassis so not sure what that means
But on the lower setting the vehicle will sit ALOT taller than a standard 109 and by fitting parabolics you will be raising it again, not by alot but it might foul the prop and flexi hoses.
There should be a cut out on the centre crossmember the prop passes through to allow the prob to move down without fouling the chassis but IIRC this isnt standard on all HD chassis.
You could put the springs on the top settings and it will sit inbetween the full height and the standard height.
Shocks may be a problem due to the HD's you should currently have fitted have alot more internal friction so they dont fade when loaded up and travelling off road.
At the end of the day it can be done but my personal advice would be to get a highlift jack, jack the rear crossmember up on one side, just past the bumperettes and hit the springs with a lump hammer to free them up and then use lots of grease.
This will give them a bit more movement but remember these were fitted so they could load 3/4 ton in the back and tow a sankey over rough ground and as such wont move unless loaded.
But i could be wrong
