First and foremost, please allow me to extend my deepest condolences to you and your family in this time of loss. These hardships are never easy.
I agree with your choice to go with a turbo motor, and the RB is a great platform to build a stout, powerful car. I too have been reading up on the inline engines in this forum, and I also agree that the RB25 a solid choice for early Z performance. You're doing a great job of documenting cost and work.