Located in 19539, PA. Not going to ship the diffs. I work right off of I-78.
1990 Miata open diff. Clean, rust free, 54k miles, early build/smooth cover unit out of a '89 built car if that matters to you. Works fine, removed to install VLSD. $70.
1.6 Miata VLSD. Ordinary condition, 150k miles. SOLD.
Miata trailer hitch. Ordinary full-weight full-steel full-rust version, Curt brand I think. It's the cheapest one available, like $180 brand new. $80? Includes ball and draw bar and all hardware. This is actually packaged to ship, but would cost you $40-45 depending on location.