Welcome to iRV2.
Your Class C tires should be 16" and that size rim allows you a lot of brand choices in tires.
Have you dealt with a local tire store for other vehicles?
If your happy with the brand and service from that store see what they can supply.
Before you buy tires though , take the unit out loaded for travel , and get the RV weighed , check the weight against the axle and existing tire ratings.
Many of these older RVs left the factory loaded to the limit and you may need to purchase a higher load rated tire.
Also have the front end components checked for worn out parts. I worked at a Chrysler dealership from 75>07 and that chassis was unfortunately known for wearing out ball joints.