I do not know about in MI, but I can say that 60's & 70's cars here in Cali go for 4 or 5 times what they cost when they were brand new.
Take for instance, a 72 Chevy Nova was $2,351 brand new, you cant get a nice one under 15k now.
64 impala SS convertible? shiiiit, sold for $2,967 brand new trying finding one under $20k is nearly impossible ( in CA )
A lot of old schools have really high resell value, & there is some like the AMC Gremlin, or the Pacer that you couldnt sell if you wanted to.
Also, there is high resell for even some 80's cars like the T Type Regal, or the Grand National,... yet I have a 1982 S-10 I use for commuting so I do not put hella miles on my Charger, brand new everything in it ( I put a brand new engine & transmission in it a few years back ) & I wouldnt be able to sell it for 1k if I wanted ( tho I put 2k alone into a new engine )