Promo based tooling, factory drawings and all that.. '60s annuals generally were pretty accurate for the bodies. IIRC, the '66 Wildcat actually has a '65 interior, AMT never updated the tool (the 1:1 had a new dash for '66). The simplified chassis never bothered me, I love the old kits for their subject matter and body accuracy..been building them for over 35 years.