Guys:
Looking for input on which auto trans to put into my '56 Fairlane. The car is close to stock, came with a 312, I upgraded the intake, carb and distributor and a few other safety/ comfort items.  The car has a Fordamatic transmission and the differential has a 3.89 gear set.  I like the power that the gear ratio provides but not the RPMs on the highway or the gas mileage.  I was thinking about replacing the Fordamatic with  a later transmission that has a lock-up torque converter.  People have recommended C-4s and C-6s and a couple claim the older AOD is the way to go.  I would prefer one that would be easy to install and would use the original shift linkage.  I do like a firm shifting transmission but don't plan on doing any drag racing. Any suggestions?

Larry Fuller