I have not heard of a R3 block failure N/A.....there has been a couple issues I have heard of with power adder guys that are making over 2000 hp, in my opinion if you want to change set ups and use the Indy heads that is fine but they are capable of mid 700 hp N/A pretty straightforward without getting super crazy and if a person was only looking to generate 600 hp with them then I don't see how the price to make all that happen would justify the meager gains.