just have a quick question can i use the main electrical harness the one that goes under the dash from an 89 mustang on my 92 . Just want to make sure.
No. The 89 harness lacks airbag wiring and has two connectors where it plugs into the engine harness where the 92 dash harness only has one. I am not 100% on this though so you may want to wait till someone else chimes in.
I agree you won't be able to get an 89 main harness (only year without airbags to have maf) to mate with a 92 dash harness without some modifications... dash harnesses from 87-89 are interchangeable with each other and 90 to 92.5 are interchangeable with each other.
1987-1988 Speed Density. All the speed density engine harnesses are interchangeable.
1989 Mass Air and No Air Bag. One year only harness. Only car with mass air and no air bag. The dash harness is the same from 87-89 on all models, but the engine harness is specific to the 89.
1990-1992.5 Mass Air with Air Bag. Fuel pump relay is under the drivers seat. The change here was made sometime in 92. All the dash harnesses for all models from 90-93 are interchangeable.
1992.5-1993 Mass Air with Air Bag. Fuel pump relay is in the engine compartment. All the dash harnesses for all models from 90-93 are interchangeable.