whats the diff btw a Planar 3 and a P3?

even though I just bought a refurbished Dual 721 (which is supposed to be here tomorrow, I'm psyched!) another Planar 3 has popped up at what seems to be a reasonable(?) $375.00, rated excellent by seller with lots (and I mean lots) of close up pictures, cartridge not included. But I digress, what is the difference between the planars and the "p's" from Rega.
The motor is the main difference between the Planar 3 and P3.
You should check with the Rega importer to be sure the upgrade motors are still available. The cost was $100-150.
so given that trade of though, putting the upgraded motor in a planar to a certain degree of course, transforms the planar to a P. The reason I'm asking because if that's all I think I'll have a Rega I can afford!
To add to what Wendell, (Narrod) said, you can buy a motor update kit from Rega for the older Planar tables to make the motor mount the same as the P3. I agree that the "plinth" itself, sounds the same.
P3 motor is mounted directly to the plinth with double-sided tape versus the rubber band mounting of the Planar 3. This provides better speed stability with the P3. The P3 plinth is beveled while the Planar 3 is a basic rectangle. I don't know that there is any significant difference in the sound of the plinths. The arms are the same.