For your build using a 400 block and mostly street driven. I wouldn't worry about billet main caps or a stud girdle. I have not built a BB stroker motor, but from buddies I race with (Most use 440 blocks) when they are around 13:1+, 7000 rpms + is when the block becomes the weak link. It seems the 400 block is stronger than the 440. I would like to build a similar stroker to what your listed. If I ever do it will be a strictly race motor and I wouldn't upgrade to the billet main cap or stud girdle. I would build it though so I don't have to spin it over 6500 and would hope for 600-625HP.