That does not look like any standard 273 damper I've seen. An easier to find 318 damper with separate pulley should interchange but there may be subtle differences that don't prevent you from running it. I doubt you'd need to change anything else for belt alignment.
I think you don't understand that pulley. The early to 69 AC bottom pulley had the isolater in between a couple of the pulleys. The harmonic balancer was separate.