spectra premium heater core issue ? / anyone recommend a good heater core ?

It's cheap Chinese trash. I'm going through the same thing on my Dakota. If you find a good USA made one let me know. Pro source models on eBay claim to be USA made but I can't confirm.

Best option? Take the oe core to a radiator shop and get it re cored?

Really? Do tell. It sure is funny that the Spectra plant is in Canada and they make some of the best gas tanks in the business.

We sell Spectra stuff at Oreilly and almost all of it has a lifetime warranty. Tell all these guys on here that have Spectra made gas tanks and other Spectra made products their stuff is cheap Chinese trash. I bet you'll get an argument real quick.

From me, in fact right off the bat. I have a 38 gallon over size gas tank for my 75 F250 and it is very high quality. You might want to check up on your "facts".