I know they're different, I know AP2 has M10 bolts, you can use a M10 (M8-1.25) x 60mm Socket Shoulder Bolt, Alloy Steel (Box of 50) to bolt it to the flange. My question is, will the cap on the AP2 prop shaft let you bolt it up to the AP1 diff flange? Because if the cap isn't interfering and it's just the bolt size difference, then you can just use those shoulder bolts to slap on an AP2 prop shaft on your AP1.