81 gmc 5.7l crank problems
 

hello everyone, im new to this site. i was just woundering what i should do, i was driving my 81 gmc 1500 and the crank pulley and harmonic balancer came completely off the crank, oil and anti-freeze started pouring everywhere, so im guessing a crank seal. what would cause the pulley to come off the crankshaft? if im not mistakin arent they pressed on? would it be easier to do an engine swap or fix what is left? :confused: