Found my dads original 1971 duster!

Well when I asked about a warranty, they claim that engine rebuilds don’t really come with a warranty, because they don’t know how the engine will be “used”. This really didn’t make sense to me. They came with such high recommendations and to be honest, a few things happened that would make me never do business with them again. I’m praying that the engine will be ok. Maybe I should email them, so my concerns are in writing
Sounds a little bit strange that they won't stand behind their work. Every engine shop I've dealt with has offered some warranty, unless it's a race engine.