They made more than one of those cabs. If you want to restore it and the guts are good, there are lots of defender/stargate cabs laying around.
I have one in a garage myself. It was SHINOBI when I tore it apart.
Save the internals. The cab is just another "part" to the cab.
If the restoration makes you happy and you feel good about doing that, then by all means, work on it.
If you have the intention of re-selling it, it's worth going price of used cabs. Restored cabs with non-original parts are not worth as much as the original. It's like a '67 mustang. It's worth a whole lot more as with the original parts than it is with bondo all over it.
I have a stargate cab I used to make a mame machine. I have another defender cab that's "vigilante".
Working Defenders run between $400 and $900 working. If it's mint, who knows, maybe $1200+
Put more than that in it, and you could have bought one.