Can I use 2 Left hand Eagle heads in this case?

The left head is a 53021616DE and the right one is a 53021616DD casting. They both have a pad for the EGR valve on one end, but that only matters if you’re building an engine for the early Aspen or Durango because they’re the only ones that need the two bolt holes and the exhaust passage drilled for EGR on the right head. Otherwise, the heads are interchangeable.

I won't need an EGR valve on a retro swap, but just want to confirm with the brain trust here.

Oil Drains are different from side to side. You will need to plug an end one and drill a new one for the rear for RH. Or, just use the middle ones and forget the end rear.

There are a total of 5 drainbacks in each head, right?

No. 4. There are no drains at the very front of each head, hence left and right.

Got it. Thanks Steff!

I thought there is an exhaust bolt difference? from Right to Left? not that it would be a deal breaker.