Ask for several references from their customers in the last year and from the last two or three years. Get their phone numbers and start calling. I may get shot for saying this, but believe what the customers say, not the salesman. Until you know you can trust the company, call their customers. Good companies will give you good customers to call and you can listen and learn a great deal.
All companies occasionally have problems.
You can find out how they handle these from the people you call. Even their good customers may have had some problems and you can learn how they were handled. Lead time is really a significant issue. We often personally deliver our engines to our customers' builders. Experience in this field is a very important ingredient in deciding from who you buy the cobra kit, and ensuring the dream becomes reality and not a nightmare.