Need help/advise before installing new harness

If I had to guess what all that is/was for... jukebox
By the way... those cheesy replacement battery terminals are junk in my opinion. If the new harness didn't include battery cables, I would invest in some. Or atleast install crimp and solder terminals.
Also, there is a better way to hang the trans. Throw a cinch strap around the torsion bars and draw it up. This lets you install the engine and wiggle to align the trans and mate with engine.