Danny71,
I towed a 2000 Miata 5-speed over 35,000 miles.

I know several Miata NB owners who have towed their 5 speeds over 50,000 miles with no damage due to that towing.
I then towed a 2010 Miata 6 speed over 16,000 miles
And this past weekend, I finished installing a towing baseplate on my 2012 Miata 6-speed.
In the past 7 years, I have helped more than 50 other Miata owners (many are still on this forum) to get their Miatas towable.
PM me if you want more information on equipment and processes to tow your 2003 Miata behind your RV.
Tim