If they're applied like normal, it wouldn't matter when the deposit was made. As far as I know, deposits are for the dealer to secure things and kind of separate out the tire kickers. So when Dingwall invoices the dealer $8k for that Z, that's that number that would be used for the tariff, even if you only owe $7500 at that point.
We'll just have to wait and see how it plays out at this point. It's not yet a done deal. For folks who are politically active and wish to express themselves, writing to reps would be... prudent. It's also possible that the tariffs get enacted, and quickly withdrawn as well.
Trying to thread the needle on this post, so that's as far as I'll take it