Best heads for Magnum 360

You better get some quotes before you do anything. You're going to be hard pressed to do a real head upgrade for $1000.

Your stock magnum heads are probably cracked. It's debatable on whether or not the cracks in these heads are a real problem.

However those heads are going to be tough to beat for a street cruiser. The type of gains you're going to want to feel, seat of pants, are realistically going to be low rpm to midrange torque. Going to be hard pressed to beat the stock magnum heads in that space, for the money you're budgeting.