I have one... like previously stated, they are machined ford production blocks. Expect them to fail in generally the same power range as a stock block. They probably (and I stress probably) will handle a bit more power but its hard to say how much more and for how much longer. If I had to do it over, I would go with a dart block so that there is much more room to grow.
I used to have a 306 LC block from DSS,It was dyno at around 440rwhp with a AOD and a P600 ProCharger. No problems with it for 4-5 years,just my tranny that is doing the meltdown. I am happy with it.
It is still out there in some guys Mustang after my car wreck.
not in my experience... the assembly & parts are good...... really all you need to keep in mind is that your buying a machined OEM Ford block. The rotating assembly is fine.