2-3 weeks seems to be unrealistic unless it's some crate motor they already have in the works that just needs to be screwed together. They shouldn't have said that if it wasn't possible. 6 months does not seem unreasonable on a custom, one off, all custom parts, good engine. But it also should be pretty close to being delivered. That said, hinky excuses would make me nervous too. Ask for pictures. That can be done in 30 seconds with a text.