I used square surface mount truck LED's from my local trucker store. For side markers I used 1" round red LED's. License plate was a tripple white LED, I cut a slot in the housing and flush mounted it. The plate clears it by about 1/4".
The whole project cost about $130.00
Got a source for your lights?
Edit: "local trucker store" I missed that the first time...still haven't seen these before...but I like them since they have reverse lights built in