Agree with planned usage being a huge contributor to block life. I have had a few 428 blocks split main webbing and cylinder walls, with well under 600 HP. However, these engines spent most of their "working lives" running very low 10 second 1/4 mile runs, with a 4 speed. Although I did not rev them really high (6000-6200 RPM clutch dump, 6200 RPM shift points, 66-6800 across the finish line), it still took its toll(s).In a mostly street cruiser, with an occasional full throttle blast lasting a few seconds or so, these blocks likely would have lasted for decades.
As for nitrous, I did play with it for a few years, in the late 80s. At that time I had a 390 and a C6 in my Fairmont, it was running 11.40s @ 117 MPH. I added a NOS "Cheater" system, with adjustable jets. With 125 HP jetting, it ran 10.4-5s, and almost 130 MPH, with no real issues, but a little later, I got greedy (easy to do with power adders), and switched to 175 HP jets. The ETs improved to high 10.2s, at 132 MPH, but after a few months, I had the pleasure (?) of sliding across the finish line at over 130 MPH, sideways, while sliding along in the oil and coolant that got under the rear slicks, when the 390 disintegrated. The 105 block had torn all 5 main webs out between the cam and crank bores, and broke the crank into 5 pieces. One cap split down the middle, the rest split right thru the main bearing bolt holes in the block. The oil pan rail was bulged out almost an inch, the flexplate teeth sawed thru the bellhousing, broke off the starter, and the C6s stator support/input shaft, etc, quite a mess. Sold off all my blue bottle stuff, and stay naturally aspirated ever since.
