As part of my Baseball Saga dynasty (see link in my sig), I've manually created the schedules for each season of the National Association as they were actually played from 1871 to 1875. Most of these seasons were played with an odd number of teams, so if you intend to play according to these schedules, you'll need to initially create your league with an even number of teams, then remove or add to get to an odd number. Once you've got the right number of teams, load the correct season file (be sure to adjust the league start date to the right day of the year).
Lastly, if you want the schedules to match up with your teams exactly, you may need to spot check with
Retrosheet to make sure the team ID's match up the games with the real life schedule (they do for me, but it's worth a double check).
I'll be sending to PadresFan, but they're also already available here:
All Sim Baseball