I have a 292 which I bought as a complete and assembled engine, I also got  a box of extra parts in the deal, and the box included a set of the stamped oil deflector plates,but none were on the heads. The heads are ECL's
Not knowing the condition of the engine I tore it down had it machined and checked for cracks,rebuilt it with quality parts, including the heads and rocker assemblies.
I have the "Build and modify your Y Block"  book and it shows the assembled heads without the deflector plates. Were these plates only used on earlier engines or were they installed on later ones to help with the well known oiling problems. Should I use the plates or not?  Any advice is appreciated, as I have a lot of time and money invested in my Y block and want to get it right the first time.