what to do with the six

The biggest issue is going to be where you stop doing stuff to it :)

General tune up stuff will be a good start but have a plan first.

X2

Recommend a good base line for starting the plan. After the general tune-up, measure compression, and check lean/rich on the carburetor. There is an amazing amount of aftermarket support for the leaning tower of power; cams, intakes, exhausts. Over at SlantSix.Org, you'll find answers and ideas that will help you settle on what you want to do.

Good luck. Enjoy!