I have always been told that 4 bolt main is worth the money. I am wanting a 351W 4 bolt main to start building up, possibly stroke to something considerably bigger. I have been told that there is no factory 4 bolt main. The only way to get one is order one from ford motorsports, the SVO block. Is this true, anywhere cheaper??? Is it really worth it, and when do you truly need a 4 bolt main?