They are worth quite alot. I would keep the original one with the car. Even though they wern't vin stamped there is a # stamped above the clutch equlizer bar boss that matches up to when the car was built. Here is a photo of mine
http://www.thefroginator.co.uk/fm-pi...%20smaller.jpg
It was the 920 th hipo motor assembled.
If you want to seel the race motor the Hipo Mustang ourm would be the place to ask value of the parts. Right now hipo motors part out for more money than they do whole.
HiPo Mustang eKschange
If you are selling the car let me know and I will post a for sale ad on the Fairlane Club of America web sight for you. You have to be a member to post there.
Larry