low oil pressure...

What is your question?

I resently fixed up this truck, it had a blown head gasket.. now thats its running. once i start it cold, the oil pressure gauge reads half then after driving 10 miles or so it drops to qutar low pressure and at idle its as low as it caan go.. and the lifters tick all the time.. do the lifters normally make a noticeablely ticking sound on this engine? should I change the oil pump??