I believe that the post "T.D." era cars will always sell at a discount with how much depending on condition, mods, economy.
I've followed A.C.'s since the early 1960s and purchased an Ace 2.6 in the early 1970's for $2,000 (now find one for less than $300,000).
A good example was the newly rebuilt highly modified Aceca selling for $60,000 while a restored Aceca Bristol went unsold with a $140,000 bid.
Recently I drive newer Corvettes and follow their values. A restored '69 L88 427 will bring somewhere in the $200,000 range. A restored well storied race version just sold for $2.9m! Similarly mid 60's 427's were nearing $200,000 but a 1 of 1 (options plus red/red color) sold for $850,000. The fact that it was the only red exterior/red interior car built added $500,000!
In my mind the market for normal cars is off right now but rare or storied cars seem to be going for a premium. A great example is the Ferrari 330 GTS which sold in Scottsdale this month. It was driven 30,000 miles had a fire and went to the insurance company before being lost for 40 years. Un-repaired and not running it sold for $2.1m. The story probably added $1.25m.. to the price!
Rarety, provinance and stories bring the money.
John