I recently did this to my 2023 GMC at4hd. I already had the bed camera so i found a great deal on a vpu that came out of a 2021 chevy 2500hd $54. I bought the front camera from ebay $53, a r-side camera, mount and lower mirror trim for the right side (you can buy every part for the mirror except the lower trim the cam mounts to its crazy) $100, and i bought a brand new damaged l-side mirror assembly that i stripped of parts i needed and some i will save as spare parts $150....i ordered the double Farka connectors from the site listed on this thread and the the same wires listed. I did drive around with only the front camera connected for a week or two and added the right side camera for a couple more weeks without any problems. Somebody told me this would not work and my screen would go blank but mine worked fine while i was waiting for a deal on missing parts. I have not programed my vcm yet... my local dealer will do it for 1hr labor (199.00)...I'm waiting because im a Acura tech and we just got a gm scan tool for the new ZDX (aka blazer ev) I was told i should have full access to gm vehicles too so i will wait a see. Either way the camera angles are only off a bit and it even has my gmc truck on the screen not a chevy like i thought it would.
Now if only the trailer cameras where cheaper id give that a try
thanks for the people who started this worked great... if i can be any help ill try