http://www.*****************/asymapp.htm this resource is excellent for all the info you're after. The clutch bell stamped may say 20 but is probably a 30 series clutch.Don't quite understand this statement"are the pieces/teeth that lock the converter made of plastic? can they be replaced by the ones on the back side that show no wear?"If your referring to the contact rubbers/inserts-no. You need them on both sides for up-shift and down-shift- normally the only time these get replaced is because they fall off.If your clutch is grabbing and jerking it's usually caused by lack of lube(dry spray lube).On the link provided is an explaination for this.If the wrong belt or extremely worn belt is being used several things will occur-slow starts,sudden engagement with slippage and total lock up of the driven unit. The driven unit has a snap ring just behind the bolt,you need to depress the outer ramp and remove the snap ring, sometimes there may be pressure on the outer ring so use caution. The shaft that the pulleys slide on may just need lubricating.