the best solution i have found, is to drill the dowel pin holes oversize, then, temporarily install the damper. this aligns the front seal, preventing leaks there.
snug up the upper bolts, remove the damper, then see what you need to do with the lower pan to cover.
address that issue, then continue to the final install with the gasket[s] and sealer of your choice.
this still means you need to temporarily install the damper, snug the upper bolts, remove the damper, install the lower cover and pan bolts, tighten everything, then finally, install the damper for good.
i know this sounds i overly complicated this issue, but it will ensure you a leak proof damper seal.
just my way of doing this, your mileage will vary.
beer