As your car was an auto,and I guess you are fitting a proper gearbox,you will need to trace and remove the autobox's start inhibit circuit.
Start behind the glovebox,you are looking for a black/yellow wire,at the point where it is interupted by a plain black,remove the two plain blacks and join the two black/yellow's together.Then carefully trace the two blacks to their source and remove that section of loom entirely.Where this section of loom attaches to the autobox selector,you will be able to seperate out the reverse light switch part of the loom.
Do not cut any wires,it's all plug in.....

Youth is wasted on the young.