What are you basing this statement on? The 305 limitation are very well known. Talk to pretty much any engine builder. History: The 305 is a redesign 265 casting of the chevy small block to reduce weight. The block is lighter then 225 inline 6 made the same year. There was no need to have a big casting when your engine is out putting 130 HP the lower weight and smaller bore helped with gas mileage. When the 305 passed 200 hp with Tune port injection we started to see spun rod main bearing under warranty at the dealerships. Per GM a failure rate was expected as they reached the design limits of the block. On the other hand the 350's only failed under warranty when something caused it to over heat or lose oil pressure. I have scraped 305's with 60,000 because no one wanted them back in the 80's. Even super budget dirt track racers would only use one if it was the only option and the needed a point for starting race that season.