I'm currently in the middle of a budget race build. It's a 91 z28 that has had a post 87 roller 350 motor swapped. Was a 5.0 car. My goal is to do a 150 shot but from everything I have read in build books is saying that a late model bottom end is only good to about 425-450hp my goal is 500-600hp. I'm on a super strict budget so as long as everything looks ok when I tear the motor down there will be minimal machine work. Basically just a bath and bore hone if I can get away with it. Is it safe to say I'm gonna need a new rotating assembly to reach my goals and not grenade the first time down the track?

 

I definitely wouldn't; especially on a set of hypereutectic pistons. You're asking for an expensive learning experience by doing that.

At bare minimum I strongly recommend a set of coated forged pistons.

 

Are you fully schooled in tuning a nitrous setup? If so, then the 150 shot by itself is not a concern on any SBC stock bottom end in GOOD condition. I ran a 150 shot on my stock LT1 (which is identical bottomend-wise to any Gen1 SBC, except possibly the PM rods) for many years putting out over 500 hp, and that motor is still healthy. BUT.....that motor was low mileage and in perfect factory condition, AND....very important to the point I want to make....that power peak was at a lowly 5100 rpm, with shifts at 5600.
What IS a concern is your goal of 500-600 hp on a tired old bottom end without a thorough rebuild. It won't last for long at that level.
Like I said, nitrous alone isn't the issue. But for your target power level, you're also going to be spinning some serious R's, and that is the issue. Even if the bottom end "looks" ok, ovalized rod big ends (yes, they will not be round after high mileage at ANY power level) will lead to bearing failure......which usually fails the rod in short order. And that doesn't matter whether they're old style SBC rods or PM rods.
I'm currently making ~660 hp with a 100 shot on a PROFESSIONALLY rebuilt stock bottom end with ARP rod bolts /re-sized stock PM rods, and also revving it to the moon. But don't try anything like that on a tired old stock bottom end!

 

Oh yeah! If you're not "fully schooled" on tuning a nitrous setup, you could shatter those pistons even before the other issues I've mentioned will crop up.

The bottom line is: Either build the bottom end properly, or lower your target.

 

Ok thank you very much. Looks like I'm budgeting in a better bottom end. And I am not personally schooled in tuning a nitrous set up but my brother is and is my go to guy for this build. Appreciate the feed back helped a ton.