5.7 with a worn camshaft?

I'm going to look at an old truck and the owner says it has a worn camshaft and runs rough.  How much power loss is caused by a worn camshaft? its an old 1975 ck1500 truck.  Will this result in a engine failure or just loss of power?  If  I get then truck would it be drivable around town with a worn camshaft?

Thanks,
Nick

i wouldnt buy it unless i was going to rebiuld the engine. and of course it wont have as much power. you could buy a new cam for around $250 or less with lifters too.