Hello from BluePrint Engines!

Where do you get your cores from?
Is there a core charge, or is that already figured into the purchase price? I'm thinking that it must be.
Do you buy cores from customers and if so, how much do you pay for them?
If a core is supplied to you, would you build that for the customer or would that not be possible?
I'm thinking of the matching numbers guys and the not too easy to find cores.
Are there specific cores that are pretty hard to find and do you have to delay an order until a suitable one is found?
(Including non Mopar ones)
Which engine overall is your best seller? (Mopar and otherwise)