The 2.9l OHV will readily run over 300 at the rear wheels with the proper amount of engineering done to the engine. Skogenracing up in Scandinavia found the physical limitations the Block in 600s range. Apparently the block itself just gives up and can go to pieces at any point over 500, which does add up to what the physical limitations of the metallurgy are. The dual overhead cam version is much more capable of reliablr power, but apparently it's a complete pain in the ass to build. You essentially need to buy both versions of the dohc and make one very ugly homunculus out of it with two T1 or T2 turbochargers. The computer that contained all of this information went up in smoke a few years ago, or all of this would be posted here along with all of the details and part numbers and machining specs.