Hello, with a factory block, especially a GM 400, the real question is, what is the target horsepower figure you are trying to accomplish with this build? If you intend to go with a higher compression ratio and the cubic inch that you specified, I would estimate with a properly matched induction combo (roller cam/intake/heads), you will be pushing somewhere around 600+ horsepower depending on how well the combination is put together. I personnaly don't reccommend using the 4 bolt main 400's, simply because the main webbing where the outer main bolt is drilled and tapped through during factory procedure makes a great breeding ground for stress or cracking. If you must use a factory GM 400 block search for a 2 bolt main and have a reputable machinist install splayed 4 bolt caps. Please keep in mind after all this trouble and machine work/exspense, you could have probably bought a reasonably priced aftermarket cylinder block such as Dart's new entry level SHP (there are many posts about this block on the forum). Aftermarket cylinder blocks seem out of reach on a tight engine budget but machine processes to get that old iron suitable for higher horses will put you into the $1000+ range, unless you have a good engine machinist that owes you a favor. Long story short factory iron is good for between 500-550HP MAX, not to say you can't put more into these blocks, many will tell you they have with great success, as have I but with great preparation put into the block. Years and years ago I built a 670HP alcohol 377cid out of a factory GM 400 with splayed caps, I wouldn't go to that trouble again though, deck plugs, splayed caps, grout block fill, pan rail clearancing for alum. rods, etc., etc. I hope this sends you in the right direction and you are doing what any good racer does,....homework. Thanks.