I worked on alot of these in the early 90s. Most likely a head gasket caused by overheating due to the heater hose failure. Hopefully you didn't add cold coolant into the overheated engine which can cause cracking of the head. In either case if it is a head gasket I highly recommend you change both head gaskets with the latest GM OEM gaskets (they have been updated several times), check the head for warpage. Change the remaining heater hoses and water pump bypass hose. Not a bad idea to change the radiator hoses too. The 454 is a good engine it builds alot of heat and so is hard on hoses and spark plug wires, more so when enclosed in a dog house type engine compartment. Good luck.
