Any tips for reseating the drive cable without pulling the cluster?

It's fairly simple to reconnect the speedo cable under the dash. I've had to disconnect and connect it while going down the road when I've heard grinding noises from the odometer. You can find a path by feel to where the speedo end on the right side of the dash cluster is located and thread the cable in the most gentle curve from the firewall grommet to the cluster, feed the square drive end into the speedo and then thread on the ffitting - hand tight is enough.

From the speedo end, you can pull the inner cable entirely out of the sheath/housing. You may find that the tranny end of the cable has a slight kink (due the the abrupt right angle turn), which you can probably straighten out. I'm always on the lookout for another right angle drive.