I’d recommend checking prices at the dealership. I can buy just about any crate gas engine or trans that I’ve ever priced with a better warranty cheaper than building or having one built
Eddie typically gives us options on rebuild vs reman. The newer vehicles often end up a better deal to go reman with the better warranty just like you said. Most basic rebuilds are in the $1500-$2000 range now. But we have had several where parts were so hard to find we finally went reman.
LKQ offers a great warranty on used ones as well. You have to pay extra for the warranty but we can get a 24 months parts and labor warranty from them and install it ourselves when we have too many sitting at montgomery trans.