There is a lot good info already posted.
The 48 is great all around length.
You mentioned it is setup for free shafting...if you use it that way and pick up another shaft and it does not have the 2nd shaft holder, it would be a good addition
A.B. Biller Shaft holder set
I have a 42 SS for shore dive spearing. A 48 or a 54 would be better due to the added reach. I also have a 75cm pneumatic for this task.
Depending on how much you will get it for, you can experiment a bit and not sweat it. If you don't like it, sell it. Billers are like old F150s with many owners and sell fast if priced fair.
I started by tieing my own bands. Even shock cords lol. Trying different bands was interesting and I learned a bit. I bought most of the material on amazon and ebay as local shops didnt stock the variety I was looking at.
Good band info
Later I ditched the metal wishbones and used dyneema wish bones. The notches on the shaft need to modified (rounded and soften the edges). Real easy to do with basic hand tools. Whats the benefit? You cant 'see' if a metal wishbone is fatigued. If it is, and breaks when you are loading it = ouch and maybe some stitches. It will be obvious when the dyneema wishbones are worn showing fraying etc.
I cut off the reversed cup flopper retainer as it acts like a sea anchor and slows the shaft a bit. The one you are looking at may be the Florida Special and doesn't have this and my point would be moot.
This post reminds me that I am overdue for a trip down to Broward.