if your ute is 4 wheel drums, then the 120Y struts, discs and calipers would be a nice, simple upgrade - as would the booster and dual system master cylinder.

i'm not the guru on diffs, but i remember reading that the ute diff is the strongest of the lot - so no real upgrades in swapping to the 120Y one. maybe the gears are a better ratio though - might be worth swapping over for some highway economy if it's not a load carrier anymore and 'reclaim' first gear i'd check to see if they're compatible or not first.

if the seats are in good condition they might provide more comfort over what might be in your ute - or not.

other than that, i can't think of much else. you could always keep the engine and trans should anything go wrong.

then you could sell the shell to me if it's in good condition