I noticed a big difference when i went from A12 to A14 back in the day with my little silver 1200 sedan. The A12 had a cam and some head work to and A14 was stock with a weber it just pulled better. With the A12 it felt like it was doing a lot of revving but getting nowhere and the A14 also revved well but felt like it was getting somewhere. as for worth depends on condition but a good stock running ones probably worth $400-$700 Then rebuilt and worked ones will go up from there.