Well at Auction ,i have attended with limited knowledge ,and seeing no olivers
Most tractors go for 75 to 200 not running .
According to tractor data Oliver were built in 1972 only. They were manufactured by Jacobson, which were hardy (also Ford lawn tractors) so parts are available. 
This a rare but not rare cosmetic lawn tractor that says Oliver 
Your asking prices are wide open , how bad do you want to get ride of them. 
Also your market you are selling to is limited to a few . Ask as much as you can but be careful your price in not based a sentimental feelings.  

I really hope this helps you , that's why I commented good luck , let us know how you do , thanks