I got a chance to get a 5.3 w/150xxx on it. The guys says it's running fine with only 4 coil packs. I've never heard of this. Is it possible?

 

Define "fine"..... down on power, missing, etc...

 

4 on each side?

 

Most likely running on an aftermarket injection system in wasted spark mode. Waste spark firing means that two spark plugs are fired at one time. When a coil fires two cylinders, one is on the compression stroke and one is on the exhaust stroke.

This is how the Cadillac Northstar and many others work.