1989 rs with the 5.0

 

found this

I think I can probably clear up the "mystery wire" problem for you. I have an 89 RS Camaro, and it has the exact same plug you showed in your photo. Mine has never been hooked up either. What that plug/wire assembly actually is, is the reverse light switch plug for a T5 (manual trans) equipped car. I think the deal is that GM just used the same harness for automatic or manual trans cars around our years. Mine also has a cable-driven speedo, and came with a 700r4 from the factory, yet that same plug is on mine, and it's factory-taped to the rest of the trans harness to keep it from hanging down. Out of curiosity I grabbed a T5 reverse light switch, crawled under the car with it, and it plugs right in to that connector. I've seen several other posts on here over the years with guys wondering what the "mystery wire" is for.

 

i kinda guessed it was something like that. thanks

 

as for subframe, it shouldnt be much more than $200 to have a shop weld on some 3/16" flat stock to make that subframe stronger. may want to get a set of subframe connectors while youre at it