I'm dealing with wiring issues on my 85 SSP, as many of the wires are baked beyond use. There's not much available yet from the aftermarket, and what you find tends to be pricey.
Here is a 8-pin plug repair (check usage, as it's marked as being for a 79-85) -
http://foxresto.com/products/view/13...re_Repair_Plug
For your 1990, here is a oxygen sensor harness for an auto -
http://foxresto.com/products/view/56...utomatic_Trans
In my case, the shop is harvesting colored wires from a good used harness (later model) to repair the existing one.