lifters and push rods

I have a bad lifter. It pumps up when it runs without the vavle cover on but the push rod has a lot of clearance at the rocker after I kill the engine. I can move it about a 1/8" up and down by hand. This is a 258 with 60lbs. oil press. at start up, 40 lbs. at highway speed and 20 lbs. at idle when hot.
Should I replace all the lifters and push rods and then set a good head on it that a friend gave me? The replacement 258 head is an '87 IIRC and has the same size bolt heads. The engine it's off of had a nut go down the intake and bust a piston but doesn't appear to have damaged the head. I get that little puff of smoke at start up,more so in the summer whrn the oil creeps thru the guides.