T5 Swap & Reverse Light

The left (driver's) side of your T-5 should have a backup light switch screwed into it. It's a simple affair that looks a bit like an oil pressure switch with two studs sticking out of it. It's a simple make (when in reverse) or break (when not) switch. Find the two wires that connected to your original backup light switch (not your neutral safety switch, if you had one). Connect them to the two studs on your new backup light switch. Done.

What he said.. You should already have the switch/sender (or else fluid would leak out of the T5). You just need to wire it up.