Bulkhead size?

[Bren2010]

I have three 2-3/8 holes in the back of my aquarium. I bought it pre-drilled.would and 1-1/2.schedule 40 bulkhead size fit correct?and if i use 2 as sumps and one as return what gph flow rate would i need not usinging overflow boxes.in going to use 45 with strainer on top?

 

[Sniperhank]

There are many pieces to your question. The gph of your pump would depend on the gph going out of the overflow, which you won't know. Then you will have two sumps with an unknown amount of flow between them depending on how they are connected.
I'd simply stick with 1 sump to apply the KIS effect. Then you will need an overflow of some sort on the system. Putting a strainer on top of a pipe isn't going to fit all of your needs.
I'll provide this quick article to assist you.
Choosing an Aquarium Overflow - Bulk Reef Supply