Both Kelley Blue Book and NADA Guides provide used values of snowmobiles. But neither have pricing for your AMF Harley Davidson. Back in the 1970s there were over a hundred manufacturers of snowmobiles, now we are down to four. Limited information is available for snowmobiles from the 1970s. NADA Guides currently provides snowmobile values for 326 manufacturers.
When pricing a vintage snowmobile, you can consult with experts in the field including snowmobile dealers who are familiar with buying and selling sleds every day. The condition of the original snowmobile and quality of any repairs may will heavily influence the value of any old snowmobile of interest to a collector.
Kelley Blue Book: 2021 to 2000
NADA Guides: Manufacturer [AMF] not listed
398cc and 440cc snowmobiles
Sales brochure, manual