If you have an auto trans a BOV is optional, it’s not optimal and your compressor will surge, but at low boost levels its fine. It’s been done without issue on thousands of vehicle’s, even ones running in the 9s.
I would not trust an internal wategate on a cheaper turbo, so if you go that route plan on getting an external wastegate. If you get a good quality name brand turbo they usually work better, but I have still heard of people having issues with them.
I would recommend a good quality wastegate as that is the only thing keeping your motor from overboosting.
As for the HY35, small, you might only be able to get 400hp out of it, and there is a likely chance it will fall on its face in the upper rpm’s, people usually run twin HY/HX35 on v8’s. . . For a remote mount like you are doing it might work ok though, not really sure. the HY35 also runs around 20psi on a stock cummins setup, not 30+.
Diesels are an entirely different animal when it comes to fuel and air. Boot is also not a measure of flow, it’s a measure of restriction. I have seen mostly stock LS1 take 22psi and only produce 650hp, while stock bottom end but aftermarket heads and intake run the same 22psi boost level but crest the 1000hp mark, the CFM is the more important number to look at.