do i need a relay?

I am changing my reverse light switch on my 1972 chevelle to mount on the transmission and have a switch contact the reverse lever. I have a microswitch rated at 5 amps.

I was planning on passing ground through the switch using one of the transmission mounts as a ground and then the other side out to the revers lights.

My question is should I use a relay in-between the switch and the light to ensure i don't draw too much through the switch?

Reversing lights use a 21 watt bulb. Say two on your vehicle = 42 watts, allow for wire losses down the length of cable, say 48 watts, then 48/12 = 4 and you can measure this on a DMM to make sure but at this point I would say you're OK.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thank you that's what I was thinking but I wanted another opinion

Just to make sure remove the wires from the switch, set your DMM to the 10 amp setting, connect the black lead to the switch end of the reversing light cable, turn on your ignition and connect the red lead to the supply side, bet you get a 3-4 amp draw.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Ya once I get the car closer to being ready ill test it

FYI - I usually use a relay anyhow.
But if your switch is cheap and easy to replace, worry about it if it fails.