I looked through the tech archive & couldn't find any info on this.

Are slant 6's internally/externally balanced (the one's I've looked at look internal) and does that vary from year-to-year, size to size, or?? Looking at putting a 1975 225 on to a 1964 push button, 904 (off a 170) and wondering if there are any balance issues or TC/crank flange fitment issues? Thanks!