Welcome to the Forum!
Here is a link to NADAGuides with a list of 1983 models:
https://www.nadaguides.com/RVs/1983/...1L-D-S/4027137
The prices are for those models in average condition as delivered from the factory. Options can be added on to the base prices. With your modifications and restoration you will have to come up with a figure that you feel is realistic.
You should give your approximate location in your post and maybe a way to be contacted. Suggest that inquires be sent via the forum's Private Messages to keep things private.