Did a search and couldn't find my answer so here goes:

I am swapping in an LS1/T56 in to my 73 TA. Currently I have the engine/body harness/computer from a 98 firebird. However, since the body harness came from an A4 I was wondering if I could just replace it with an M6 harness from a 99 on up. Are there any differences between the years and between the Camaro/firebird versions that might affect my plans?

 

since your using a 98 computer you would need the six speed harness that goes with that year...I am pretty sure that a few pins in the harness plug were moved around after 98 causing the later production years to be different but they can be re pinned and moved around if you want to take the time..

 

your going to need a 98 harness for a 6-speed car. I could probably get you one at my work PM me for details. A 98 harness is unique to the year. It has several different plugs, different ebx plugs, and to convert would be almost impossible without encountering electrical gremlins down the road.