When I wanted to add a little more pep to my 66, I went with the Vortec heads and a Edelbrock Performer intake. The only thing I didn't like about it was the appearance of the valve covers. You have to change valve cover to one that the bolts go through the center of the valve covers and everyone assumes the engine isn't original. I had 3:36 gears but I think your 3:55 are perfect.

http://www.C3VR.com/member_uploads/8301_8400/8356/rearn2go66engine.jpg

Have the distributor recurved. That is what woke my L48 up the most before I spent lots more money on the rebuild.

Greetings:

 hey buddy,,souperup,,,,with a set of edelbrock performer heads, a good edelbrock carb,(no need to change the hood)a mild cam,and a 3-73 rear gear,,it wont set  the local track on fire, but it will give you that ,,whoooa thrill when you gooose it,,rd

Install a set of heads with 64cc chambers.  This will increase the compression ratio, which increases torque.  Your current ones are probably 76cc.  Install an edelbrock performer intake or equal.  This one has a low enough profile and breaths well.  You can use your Q-jet or install an Edelbrock 1406 carb.  You can always install a larger cam designed for torque and update to electronic ignition.  All these will increase HP and keep it mild instead of wild.

Great information...thank you very much.