Robert,
Do you have the correct size plates for the unit and 'PASS' sign?
I had a set made here in Gympie, for $24.50 each.
They are the size of 8&1/2" by 9&1/2", which is as Tony Wheeler has stated.
Mind you, he would have made em in 2ft by 2ft if I had asked

.
Anyhoo, when I picked mine up, I asked if he was interested in making more and he was happy to do so, if anyone requested. They do take a little time to get right, so I don't begrudge the $$$. I would imagine anyone with metalwork skills & a folder could do same without problem if talented. I'm not, so I bought them instead.
In the photos that Tony W. posted, I suspect they did censor the TAC & bridge plates deliberately. Pity! When I was investigating the correct signage for my vehicle, I scanned through over 200 pages of military regulations and associated BS, before I was able to determine what should be on the unit plate. You are lucky that Tony W saved you all that crap

That must be worth a beer some time in the future.

Once I thought I had the right sequence of numbers, this photo confirmed that I was on the right track. Note the sign by the parade route. This shows the 29/46 Infantry Batallion being reviewed by a member of British aristocracy. Somewhere in this photo (possibly) would be my Father.

That's him standing with both arms up and the slouch hat in right hand. This photo shows the day they were told Japan had surrendered. I think it was Keith that spotted the CMP in the extreme background. Dad was a driver/mechanic so it was very likely that that was his charge!
It is great that you are considering adding the signage of your uncles unit to your vehicle. Do please post any interesting findings from the requested documents, when they arrive, and of course, photos of the unit plates too.