If you bought two adjustable lubricators why not put one before and one after, if you have room and the money.
If not you could always make one lubricator with two pressure chambers and supply both sides without comprimising the control valve.
That said, the reason you put the lubricator near the engine is to keep it hot which uses less oil, but the same can be said by keeping it close to the boiler, which would also lubricate everything for you.
Greg