David, are you using a factory block? You may be approaching the structural limits of a stock block. They like to split in half when you get up around your power and rpm levels.
If you're wanting to go with a hydraulic roller, keep in mind that you won't be able to spin it up as high as you are now. I personally wouldn't go any higher than 6000-6200 with a hydraulic roller camshaft, but KC and some others are doing it with titanium hardware, lightened lifters, etc.
Also, if your goal is to make more horsepower, you're going to either have to do it with the heads or the cam. If you keep the same heads, you're going to have to add cam, which again would put your peak hp rpm up a little higher....again not a good place for a hydraulic roller to be. However, your bottleneck are your cylinder heads. You would probably pick up a great deal of power by going to a set of AFR's or equivilent. When the heads don't flow, you have to make up for it with cam. A 288° seat duration is HUGE for a 331.....in comparison I used a 286/292 camshaft in my 428 FE....and that cam made the 428 peak at 6500. You have a serious airflow bottleneck.
Solid cams are just noisy...that's why everyone likes the old tickety-tickety sound of the old solid cam 289's and FE's.
Getting back to the block...
If you had a bottom end failure, make sure to have the block magnafluxed really good between the cam and the mains. It's very possible that you could have split the block there, causing a loss in
oil pressure...