my 87 was 2.8L stock with the 700r4 tranny. I don't have rpo codes because I swapped the interior out in 2000, does anyone know what gearing these cars came with?

I'm probably only going to be pushing ~375 rwhp after I'm completely finished with the new engine components(stock heads and intake on there now), and don't really want to take a big hit on a tougher rear end. I know the 10 bolts are pretty weak, would installing a posi unit or an upgraded gear set hold up, or am I destined to take the plunge for a beefy rear end?

 

All 87 2.8's came with 3.42 gears