I have a 1989 Bullet with bravos and a notched hull.
I would like a top end of 75 will 500HPs do it?

I think you will need more than that - that'a a heavy boat! I am running twin 420 hp in my 28 cigarette and getting low 70's.
I would say you would about 550 hp.

AC

i also have an 89 bullet w/ notched transom and bravos. i am running 454's that are stroked to 496's w/ merlin heads, isky 275/284 roller cam, b&m 250 blowers and nickerson 1280 carbs. not sure about the hp but around 600-650 supposed to be. we are running the new motors easy right now but w/ only 2lbs boost and 28p bravos i hi 75 gps easy at just under 5000rpms. the 89 bravos have a very blunt nose and according to hydromotive, they arent good at those speeds. just put their nose cones on and noticed a big handling difference. this weekend we are going to up the boost to 5 lbs and play w/ some props. this combo needs to turn about 5800 so i expect to see low 80's when done. will let you know!!!

I had a 91 with 550 HP that would do 78.4 GPS in fresh water. I sold the boat and the new owner put on new style braovo's and I was told he picked up 4 more MPH.

I have new style bravos on it

90 Bullet with 650hp. Dyno......

Im pulling 78 mph. {GPS} with the timing set way back and not so great 28 Bravos...The motors are broke in now so Im going to try Labbed 30s and timing back up to 36.......Notched Transom,New stye Bravos.....