True. A 2-1/4" headpipe became standard in '76, and is a much better choice—all benefit and no drawback (no, the underspecified headpipe does not "make lots of torque"). But the car should probably be put together in running condition before exhaust system upgrades described earlier in this thread are worth contemplating. :-)
An electric fan is a far down the list of cost-effective upgrades; it's expensive to do properly (and unsafe to do halfassed), and the benefit is small—definitely not low-hanging fruit.
Stock rear axle ratio in '64 was 2.93 with an automatic, 3.23 with a manual transmission. The big tires are definitely contributing to the sluggish acceleration, especially since the previous owner probably didn't swap in the correct speedometer drive pinion when the oversized tires were installed.
