Yes indeed. I have (and are in the process of selling) an 02 pro-x 440 race sled. It is a great, fun sled, but I needed something a little more racy yet, I bought an 04 pro-XR 440. But anyway...
It was fun to ride. I left the shocks basically stock. It will beat you up a little on trails if you sit down for long periods of time and the trails get rough. Your friends will be mad at the speed you can take the bumps though. The 02 motor ran great, and I never had any problems with it. Pump gas heads, and the trail size tank and you were in business. The jets I would recommend for the trail would be ~310's for safe to 0F and like 1000ft altitude. I ran with 310's and 300's most of the year and had no problems. Sled was snappy also, except when it got pretty warm out. Keep the idle high though, if it idles below 2000rpm it loads up and gets slow out of the hole.
You can do a 660 kit on this motor. But it will be more expensive. You can't just bore the 440 cylinders, you need 600 ones as far as I know. You will also need the top case half machined for the larger size pistons and bore. The stock tmx34 carbs will be a bottleneck with the 660. Finally you shouldn't use the 440 pipe with the 660.
One caveat is that they are pre-mix. But you can just buy a small block oil pump and an oil tank and it is a fairly straightforward conversion. I have a friend that did it. If you need more details I can find his how-to he wrote on snowest.
The pro-x chassis is a strong chassis, it can withstand some serious abuse. Mine took a few good hits and the previous owner gave it some good ones also. The shocks are not clickers, so you are stuck with a stiff setup all the time basically.
Recalls or problems, hrm. The chain tensioner was built poorly and the pin in it can slide out and marr up the chaincase cover. Polaris says to a chisel type punch on the ends of it to deform the metal to hold the pin in. Also, on all the edge/prox chaincases there is the possibility of the tensioner threads getting ripped out. You mainly see this on the snoX sleds though, that take huge shock loads. I, and many others, have had to helicoil the case.
Anyway, here are two pics:
My friend's and mine, both pro-x 440's, only difference is he made his oil injected, lower riser, no studs, and a different steering hoop setup that moves the bars back farther, loosing some rider-forward.