Any of the standard Futaba servos ought to work just fine with your receiver. If it happens that the additional servos are dead (it happens sometimes) most of the standard Futaba servos should work. Actually most standard servos will work but be careful, I think it's Airtronics servos that have a different pin out. The Kadet isn't that picky about servos but you will want to use the same servo on both ailerons. Assuming that your second receiver is compatible with the Conquest transmitter you can probably find the correct receiver crystal on ebay. I have found that a cheap servo tester is a great tool to have when sorting through the Big Bag of Old Servos.