well.....the slant 6 cars are at the very bottom of engine options. In my opinion a "numbers matching" slant 6 will never make any difference in the value of any slant car (no offense to anyone), however, there are many things you can do to get decent power of them. a set of headers for starters, a super six 2 barrel swap or even a 4 barrel intake, ignition upgrades etc etc. there are a ton of threads about upgrading and improving the /6.