Very common problem.I find that maybe 1 in 5 will work without some scraping etc.Sometimes you can press one in and it will be tight remove it and put another in and its ok.One thing that helps is to use a babbit cam bearing.They are the ones that are pressed into a circle and have a seem that you can see on the back side.Factory bearings were of that design.They conform to the block better than the seemless Durabond type bearing.I use an old cam (check straightness) that has a groove ground across each journal.Short of align boring the bearings after they are installed it is the most accurate and easiest way to fix this problem.

One more item that helps is the tool that is used.The Kent-Moore style with the solid rubber sleeves works better that the old style Lisle tool with the o-rings.This is what most shops use.The new Lisle tool has been updated to the solid sleeves style.

Lastly, always install the front bearing from the rear of the block.