Make A 90-93 5.0 Engine Harness Work With A 89 Dash Oct 29, 2017Hi, is there a way to make a mustang 5.0 1990-93 engine harness a3m computer work with a 89 dash harness? Please let me know if there's anyway to make this work other than buying a whole 89 engine harness, thanks!1990 wiring issue | Mustang Forums at StangNetMay 17, 20181990 Mustang Gt fuel pump has no power.. | Mustang ForumsAug 15, 2013HOW DO I CARB. MY 5.0? | Mustang Forums at StangNetSep 10, 200990-93 5.0 hp factory hp rating. | Mustang Forums at StangNetJul 05, 2007See more results 1990 mustang wiring harness | eBay Find great deals on eBay for 1990 mustang wiring harness. Shop with confidence. Skip to main content. eBay Logo: Shop by category. Mustang 1990 5.0 Engine wiring harness COMPLETE 87-93 GT LX MASS AIR. Pre-Owned. $149. Time left 1d 11h left. 0 bids. $200. Buy It Now +$27 shipping.