I don't have a lot to add on the battery, except that getting a good initial charge is impossible with a little 1 amp trickle. Use a big charger, or take it to an auto store and ask them to charge it for you. I bought a big charger from Sears .. $150 or so. Also, I had a poor connection at the red high amp connectors behind the dash. Just had to bend the tangs a little to make better contact.
Somewhere it is written that on the speedo cable, you need to remove about 1/8" from the tip that goes into the gauge. So the brass ferrule will seat against the input of the instrument. Do this with a ceramic cut off wheel on a dremel. After cutting it off, bevel deburr it a little on the four sides with the ceramic wheel.
At the tranny end, make sure you are using a reverse driven gear for a Tremec tranny, not the OEM Mustang or Cobra gear, which is for a Toploader. Yell if you need the part number and I will dig it out of my pile. And make sure the little ($10) spring clip that holds the gear on is in place correctly. I had to experiment with tooth count to get the speedo reading right. I ended up with 18 tooth for a 3.31 rear and 26.5" tires.
Congrats on finally being on the road! Now the fun begins! While you've been puttering all year, I'm on engine #3, tranny #3, differential #2, clutch #3 ..
You're never done
Sam