Congratulations on owning the greatest spring pistol ever made.
I have an early one s/n 45047 and it too is nearly mint.
If all is in good nick it should be doing about 450 fps with light to medium wadcutters, so about 3.5 ft.lbs.
Mine is a little twangy (probably dry inside) but runs bang on the money at 3.5. The piston seal is steel and should never wear out. They were designed to run almost dry of lube anyway for maximum consistency.
Lots of info on this thread
I think a short barrel version with scope rail (like the one on the thread) tuned to 5 ft.lbs would be the perfect air pistol. To answer your next question, no I've no idea where to get the rails but if you find out let me know I suspect that one was custom machined.
“We are too much accustomed to attribute to a single cause that which is the product of several, and the majority of our controversies come from that.” - Marcus Aurelius