If you were to buy a new SPF roller for, say, $74,000 (a number I use only because Dynamic Auto West in Redwood City, CA says they have one for that price), add a $15,000 crate motor, $13,000 RBT transaxle, and pay somebody competent another $15,000 to put that together you'd spend $117,000 for a brand new one. However (and it pains me greatly to say this) the last couple that have sold at auction both went for well under $80,000. So with those two numbers in mind if I were in your situation (and I was, once) I would start "networking" to find a current owner who wants to sell his. You probably won't get it for $80K, but you probably will get it for well under the cost of a new one. The difference between a "new" one and a "used" one is likely to be a few thousand miles on the odometer and the fact that the "used" one has now been thoroughly shaken down and will provide you with no surprises, whereas the new one is likely to have a minor glitch or two before things settle down. I also suggest calling the other SPF dealers (Rick Muck springs immediately to mind) to see if someone has a roller on hand they'd like to move off the floor.
One more thought; I learned at a visit to SPF a year or so ago that they sometimes lease them. So another approach would be to look for one that's about to come "off lease".
Also, when I was looking for mine Dennis Olthoff new of just about everyone that was for sale that I found on my own, so you might start by calling him.
Now, let's hear something from the RCR, ERA, CAV, etc. fans.