I've never bought a transmission before...

This car will be a weekend cruiser with the occasional summer drag.

Original Dart -
Where abouts in California are you located?
Here's something else for you to consider - if you're not a Mopar purist - depending on your budget.
You mentioned your car will be a weekend cruiser with an occasional blast down the strip. Have you considered the benefit of a 4th gear overdrive?
I had a 200-4R tranny built by Extreme Automatics (www.extremeautomatics.com) to go behind my smallblock since I want the best of both worlds...freeway cruising capability and drag strip acceleration. Give them a call and let them know your application.
The 200-4R will fit in an A-body trans tunnel without major surgery. There are several threads available in FABO about this.
I requested my tranny to be a reverse-pattern, manual shift with a lock-up converter. I'm planning to run a 4.30:1 rear gear in my Dart. The 0.67 OD of the 200-4R will let me cruise on the freeway like I've got a 2.88:1 rear gear.
Also, the 200-4R has a better 1-2-3 gear spread than a 727 and a deeper OD than any of the Mopar OD transmissions.