The engine on the 8 is supposed to be canted. The VS is put on perfectly straight and the engine is canted to overcome P-Factor. I originally thought about the mount, but with the firewall holes lining up pretty well and the back of the spinner centered, I believe it is right. I posted the pics to see if anyone else could verify theirs is about the same.
I also thought maybe the 390 jugs were slightly wider than the 360, but I understand they are identical. (Will confirm with Barrett tomorrow morning.)
I have a few ideas on making the cowl work. While I use a 1/4" spacer for fitting, it measures about 3/8th now, so I can fill and drill the rear of the cowl and pull one side out like Bruce mentioned. Someone else suggested placing a spacer and applying some heat, then letting it cool. I may also be able to remove some materials from the spinner holes and smash it down in the center to bow the sides out.
I'm still interested in confirmation of my engine mounting measurements and will call Van's in the morning also.
Keep the ides coming.
Bruce, as I said, spacing is about 3/8" back from the spinner and centered. Though centered actually leaves about 1/8 to 1/4 on the sides to play with.