Where can I buy a reliable remanufactured 318 for 1971 Duster?

Hey Ken,
I suspect part of this issue is "down time", and perhaps building a similar engine for a like for like swap helps to eliminate that.
There is a machine shop not too far away from you in Lake City called Adenaline performance who speaks mopar, and can build you a long block of which ever engine you decide upon. Not sure that route will be cheaper than a crate engine from Jasper, but worth a call.
I always tell people that ask, that Blueprint is a good deal per horsepower, but I understand that you are after a stock rebuild.
If you have any interest in engines and especially mopar, please don't give up on the hobby. I hope things work out with this build!