you modulate the pump with crancase preasure. so you can dril the block and have 2 output lines or split the actual one and feed 2 mikunis.
Now jose you have 2 pumps right now, a mechanical and a evinrude pump. The problem is that with the mechanical you need preasere regulator, and you have it.
I would suggest get rid of the preasure regulator. eliminate the mechanical one and mount 2 mikunis in parallel. you have 1 carb so the round mikuni have 2 output. use the single out put pump but 2.