Your combo isn't all that wild, thus the original tune in the carb is where to start. As you're chasing the best ET/MPH, change ONE THING at a time and keep good notes. A log book is your friend. A better friend is a weather station as even a few hundred feet in DA can effect power and thus ET/MPH.
Love the old school combo! If it's in a 3000-3200 A body, with the RIGHT converter and traction, you should be able to generate a very low 12 second time slip.
PS - (If I'm reading correctly that it's a use motor) While it's out and after it's bolted together, a leak down test would be on my to do list. It's worth the piece of mind to know it's sealing up well.