Aren't the clean out ports on the right hand side of that boiler.
By code you can't have a shut off valve between a relief valve and the pressure vessel, you have a valve after the combo.
Need combo's blow off piped down toward the floor.
Also should have shut off valves on both sides of the circ.
I though about that relief valve pipe several times and still forgot it. Next time I'll pipe the reducer above the valve to tank. There is a check avlve in the background for supply, by the hanging strap, but the reducer valve states in the paperwork it can do backflow duty.
Just to clear the air a little regarding your post, it is not really advisable to move the return to the rear tapping on the Burnham V-8 water boiler. We made provision to open the swing door with the front return pipe by providing an articulating or offset hinge assembly on the door. By removing the two securing bolts and/or nuts you can pull outward on the door and shove it to the left where it will swing open clear of the return pipe.
The return pipe really needs to be in the front to provide proper flow and heat transfer capability of the water as it flows through the boiler. Quite a bit of effort went into the development of the special door hinge to achieve this. Some other manufacturers install an offset elbow to have their return pipe clear the door and they risk having those swing joints loosening during shipment. Hope this helps.
There is some space on the backside of boiler (not 30") which would be nice to have more space there. Unfortunately the oil lines are in the floor and can't be easily moved to turn boiler around, the box was put there by ho the keep them from being damaged. I have had to turn things around for access or pull away from wall.
Next time I coma across one of those floor lines I may try cutting a groove in the floor to lay the lines down flat in to keep out of harms way.