I'm not too knowledgeable about American Iron. I can give you a few pointers though.
If you've got the engine apart, the best way to check compression is to measure the combustion chamber volume. The pistons being flat-tops make this easier still. Here's a link where you can input the measured details and you'll get your CR with a bit of elbow grease.
http://www.steigerperformance.com/PRODUCTS/sp90005.html
Generally, you've got three types of pistons as concerns the crown shape:
Flat-top
Dished
Domed
The dished and domed are used to decrease and increase compression ratio respectively. An increase in CR should be accompanied by an in crease in octane rating of fuel and/or timing changes of the ignition.
As for the manual, didn't you say you already had one to fit? If not, refurbish the auto that came with it and fit a torque convertor with a higher stall. It's the toughest thing going. With a manual, you might end up with un-optimised ratios. And if the car came with an auto, you'll change the pedal box as well?