I have searched all over the internet and only found a few topics written in car magazines.

I used one a couple years ago in a 496 build, and had no problems at all. I sold the boat and it was still running strong this year. The crank took a little bit of polishing to get the clearances where I wanted them.

Now I am building two more 496’s. The last one would spin 5,200 with no problem. I had good H-Beam rods and JE Pistons. I have good exhaust and cam will again be from RMBUILDER. Heads will be brand new, just have not decided on which ones. I used Edelbrocks last time, I might switch to Iron Eagles from Dean G.
I would be happy with 450-475HP

I would just like to hear from anyone who has USED them.

Go forged. For a few hundred dollars, it's not worth the worry. You are probably going to make 500 + with that parts list.

I have used cast cranks in race cars that were spinning a whole lot more that these boats ever see and never had a problem, would run one with no second thought in that app. Rob

I've been running scat nodular steel cranks for the last 6 yrs in a twin engine appl. 1st 4 yr were n/a about 550hp 52-5300rpm. This yr and last blowers w/ up to 6.2psi and 9.5:1 static compression spinning as high as 5600rpm. Maybe 700hp but never dynoed. No problems. I do typically keep the rpm down around 5400 due to the cranks. If you want to spin them up around 6k I could definately go forged. 5500 and down, cast is good if the assembly is well balanced.