I can't take issue with anything Rick L. said -- and I dearly enjoy finding fault with Rick's posts.
I don't think you can even get a "one-legged rear" in an ERA, they all come with Power-Lok LSDs, so don't worry about that -- just decide between inboard and outboard. Regardless of how your mechanical skill is now, there's a good chance that over time you'll become a pretty proficient Cobra mechanic, and the ERA outboard rear is fun to play with. The rods and sway bar are adjustable and the mechanical configuration of the entire rear is a simple, elegant design.
Rick L. -- you never proffered an opinion on whether zerk-fitted U-joints were less strong than the "lubed for life" U-joints. What say you?