Anyway, for the OP... This is from Bel-Rays website to help clarify weights of motor oil vs gear oil . "A 10W-40 motor oil’s viscosity is actually similar to the viscosity of 80W gear oil, and the viscosity of SAE 10W-30 is similar to 75W gear oil."
If you got that gut feeling about them then trust your gut and find a Banshee that is for sale locally where you live or one that is in a reasonable driving distance. I found my mint condition 05 Special Edition Banshee for a good price from a local collector.
Good Luck!