After fitting my MkIV nav computer, just to add 100% accuracy I want to run the speed and reverse signals.

What pin on the BM54 on my 2003 car will I pick the speed signal from?

Will it already have a wire on it?

I am happy enough tapping into the reverse wire.

And what pins do they have to run to on the burgandy plug on the MkIV?

Thanks

Terry

PS Is there anywhere on line thats good to buy the parts from?