It isn't really feasible to turn a Pantiger into an accurate Panther, even the upper hull and turret are extremely inaccurate. As others have said you can certainly make them look very good (I have seen some stunning ones on this forum) but converting it into a regular Tiger I would probably be the best bet if you care about accuracy.
I did have an idea a few months ago though when I saw a Pantiger in person for the first time:

- VK 45.02 (H).png (276.49 KiB) Viewed 174 times
VK 45.02 (H) (Image from it's Tank Encyclopedia article)
One of Henschel's failed designs for the Tiger II programme. It was never built and quickly abandoned in favour of their "Tiger III" design, the VK 45.03 (H), which beat Porsche's failed VK 45.02 (P) and became the Tiger II we all know and love.
The pre-production Tiger II turret is available in 1/16 scale and whilst it would still require some surgery to get the hull correct it would be easier than trying to turn it into a Panther albeit still harder than a Tiger I conversion.