The only thing special about a LTD is....
Handlebars (can be bought)
Cockpit with tach (very hard to find)
headlight fairing (impossible to find)
Paintjob (impossible to replicate)
Sealed bearing mags (hard to find the front with sealed)
Key kill switch (easy to buy and install)
The paintjob and the headlight fairing is what really does it though. so basically you have a puch magnum MKII. its not your fault that it was already painted shitty. but you dont really have anything special unless you have the cockpit and tach.
and then yeah a magnum is worth very different things depending on where you are. in ohio 400$ tops unless you did a REALLY nice paint job. in San Francisco, that thing could go for 700-800.
If you still had the original paintjob it could be worth A LOT! depending on how well you marketed the sale and the condition it could easily sell for 800$- 1500$. I personally would pay over 1000$ for a LTD magnum in fair condition with the tack and headlight fairing.