I've never used them, but if they're from NPD i wouldnt worry too much about quality, in my experience NPD is one of the best companies out there for quality
NPD sells the same panels as everyone else, correct? Its not like they have their own sheetmetal factory. There are good repros and bad ones, I imagine the good ones that eveybody sells all come from the same place.
I've got one, seems like a nice peice of metal. I haven't pulled the original off yet to be able to compare it to the stock sheetmetal though. Hopefully next weekend that will happen.
I used NPD for my 67.. the body shop that did my work had to put some effort into making them fit right. But I am pretty sure that is standard with almost all sheet metal replacement.