I also own a 1975 710, mine is a base model 2 door sedan. When I say base model I am referring to the trim level, it does not have door sill's stock, NO wood grain dash, and NO console stock. I bought it as a stone stock little old lady car, not very stock now.
I am always on the hunt for parts, they are not as plentiful as for a 510. I do have some spare stuff but not that much interior, but I do have a set of stock front seats.