I install custom exhaust systems and have a Washington State emission certification and will say it again, it is against Federal EPA law to remove/modify an emission part on a vehicle for on road use.
What if you get a car that has no exhaust...or, no engine/drive train and the owner goes from there, down to the shop, like yours, where do you stand leagally?
Looking at the vehicle as a everyday driver the owner will use. That should be noted.
I wondered about this from state to state. Not mention, leagally speaking, if I purchase a car like this and bring it into my state. Hummmmmmmm