The condition sounds good. Crusty on the outside is OK as that is easily cleaned off. Crusty on inside is less good but the ease of motion of the pistons bodes well.

Following up... to get the throttle shafts out you do not need to drill/tap out the taper pin, just remove everything else from the shaft. Only way to really tell the level of wear is to visually inspect. Visible wear is too much wear. If you don't have inside micrometers (who does) inserting a new shaft in the body and checking with wire gauges can give the wear indication of the bushes. Typically, as stated, if the bodies have the replacement bushes you can assume little if any wear. If the bodies have the original bronze bushes and the shafts are worn then it is best to have the bodies re-bushed (you can often get away with re-using slightly worn bushes or have them over-bored for over-sized shafts... if they are worn you can cross that bridge).

Also, pop for the $35 dip-can of carb cleaner. Stuff is really nasty on your skin and on rubber so use gloves to protect your hands, clothing you can toss and eye protection... scratching parts with brushes always makes splatters. On the positive side the stuff gets carb gunk off better than anything else. Rust on parts that can rust is best blasted off or (if delicate) use naval jelly.

It really isn't difficult but it can be fussy. I've done it many many times (even zenith-stromberg CDs) successfuly. Only part I have to farm out is those darn bushes.

Mike!