Make sure it really is a VMF. There are some Mexican made ones out there. The Mexican Mustangs had a flat seat, while the VMF models had a ribbed seat. You can find them unrestored in bad shape for about $100 to $150 the last I checked. I did one a few years ago. The big factors on cost are if the drive train is present or not. The front and back units cost about $50 each. I think by the time I had the parts (including a new steering wheel, new tires, bushings, seat, windshield, luggage rack, etc.) I had a couple of hundred in parts to put it back together.
The place to look for reproduction parts is called Blue Diamond Classics:
Hey I just saw thoes in a catalog I have at home, not the AMF's but some repo's, hmmmmm, I think it was........ohhh, I cant think. Maybe like mustangs plus, or NPD even, I saw them listed for $249.00, white or red. Below are some links for some vendors I found on the net that sell them also: