They sell the long bed and screw for the 4400 lathe. Give them a call. The beds are the same on the long and short bed versions other than length so everything should just bolt right on. Easy-peasy and cheap.
I would jump on it, B. Then you'll have both a long and short lathe. There are many times when having two lathes available will make a project possible. The long bed lathe is incredibly useful and allows you to make stuff that you wouldn't ordinarily think a Sherline lathe could make.
I picked it up last night for $300, which is about what the parts to upgrade my 4530 would have been. It's actually a custom industrial setup based on a 4400 and it took me a little while to figure out what I had. In addition to the stock lathe, it came with a 6520 dove tail headstock (that was apparently used as a tailstock) and a riser plate and pivot pin to raise the factory headstock to the same height. Both headstocks have spindles with a 9/16" ID and no Morse taper (Sherline p/n 40239). This should allow me to pass through stock as large as 14mm, which is a big plus. It also came with 2, 3-jaw chucks.
In order to use the tooling I have, I'm going to lower the headstock to the original height and use the standard tailstock. I can always change the configuration if I need to for a special project.
The cross feed table had been modified, so I'm going to replace it. I need a few small parts, but I'm going to end up with a second lathe with much improved capacity for relatively cheap money.
Sounds like a nice score. You can also get or make a riser if you have a QCTP, or you can get or make the higher set of tool post. I did that for mine. That way you can do a little bigger items as well.
The riser under the headstock is .435", which is between 11mm and 7/16". I have a couple of QCTPs, so making a matching riser seems like a great idea. I can use the dovetail headstock as a tailstock.
There's another option, too. I have the standard headstock riser block and QCTP riser block, but not the tailstock riser. Perhaps I'll get one and if it looks like I have a use for the dovetail headstock I can make a custom riser for it.