I have found installing loud pipes eliminates most annoying mechanical noises LOL
One thing you can do is to get it warmed up and rev up the motor out of gear to about 2700 rpm thats about cruise rpm and see if the noise is there, if so then you can check around the motor for the sound or have a bud help.
It could be something loose like a floorboard or heatshield or a bolt
If it's mechanical in the motor then you can take a screwdriver and press the tip against the cam area, the heads, rockers etc and the handle to your ear, acts like a stethoscope and you can really hear the internal noises.
DOn't try this at 60 MPH though!
Give the ol gal a good washing and wax and polish, that's the best way as you go over every inch and look for loose parts,