What's it cost to re-core and add a core?

I have a 68 Barracuda that originally had a 318 engine. The plan is to build a 408 next time around. I want to make sure my radiator can handle this. I brought it to local and reputable radiator guy and was quoted $860 to re-core and add a row (make it a 3 row). Also a new lower tank will be required to fit the third row. Does this price sound right? I called Cool Craft and their top of the line radiator is $750. I wanted to run this price by you all to see what you think.

Thanks,
Eric