5.0 rebuild

Hi all, so first off I have a bit of a weird build that I need some help with. I recently bought an 87 Mazda RX7 that was swapped with a 95 Mustang GT motor ("drift" car). It runs, it drives, but fuel pressure was low and oil pressure wouldn't pass 35psi regardless if I got to redline or not...

I have a 1989 mustang GT 5.0 manual trans I believe the car is bone stock besides a cold air intake. I have never attempted an engine rebuild but. I have always wanted to my goal for the motor is to make around 400rwhp I don’t want it to be a daily driver but I am seeking reliability I wanna be...