It's been my experience (2 guys I wheel with) that if your jeep gets ganked or wrecked they won't cover any mods or upgrades. This might vary between users. On top of them not covering upgrades, they jacked up the rates a little by making the claim modified jeeps are larger targets for thieves and are "not as safe" as standard stock vehicles.
My insurance company will never know of modifications to my jeep. Hell even stock vehicles they don't want to replace stuff. If a rusted out YJ goes off a cliff, $1000 tires, $2500 per axle, $500 springs and shocks, upgraded wheels, top, fenders, and whatever else....gone. You'll get book value, and that doesn't even pay for the tires
insurance companies and modified vehicles don't mix well. You roll the dice playing with them. At least in my neck of the woods.