You can get a not too old Mustang GT for that money. That will give you the most go for your dough, and that V8 rumble you're looking for, plus it works from the day you get it. If you do an engine swap into an Exocet, you're going to wind up doing some fabricating and a lot of testing/debugging, especially getting it to handle. Track time is precious and you don't want to spend the next couple of seasons trying to make your new car handle, and balance is everything on a road course. The other thing about an Exocet is that you'll be driving it mostly just to and from the track, it's not something most people find pleasant to drive on the street.
Here's what you can get for
10 grand. If you've got an itch to work on something, get one with a lot of miles on in and swap in a crate engine. I realize that a Mustang doesn't have the neat factor that the Exocet does, but it works from the day you pick it up.
If you are considering a four cylinder kit, do look at the Factory Five 818.