Seems if you want to stroke your engine, you could install a flat plane crank , (have to replace the crank, anyway) and maybe OHC heads, and have each bank firing like a flat plane four, with the left bank firing 2, 6, 8, 4, at 180 degree intervals, simplifying your 180 degree header routes by keeping them on the left side, and the right bank firing 1, 5, 7, 3 at 180 degree intervals, (90 degrees after their crank pin mates), for a firing order of 1-2-5-6-7-8-3-4, again, keeping the 180 degree header pipes all on the right. (maybe the right bank firing would be 7, 3, 1, 5, for 7-2-3-6-1-8-5-4, but still all the 180 firings would be on a side. I'm trying to do this all in my head, so I may be off on the flat plane firing orders, but not the 0-180-360-540 positions.