Help: what is a good brand heater core?

[luvbowties]

I have replaced heater core twice in my '66 C10. It is a Spectra Premium brand--the only 1 sold by AutoZone, Advance, Rock Auto. They develop a leak, very slight(but I've never seen a "good" leak) where hose nipple is soldered onto tank. Used care installing 1st one to NOT over-stress applied force when installing core and esp. sliding on the hoses; used double-care on 2nd replacement!

Anyone else having this problem? They replace it w/out question, but I'd rather be working on something offering more reward. What brand have others had good service from? Where did you buy it? I'm using a 14# cap and if I find no other solution, I'm gonna try a lower psi cap, altho' I think 14# should be correct.

Thx for any known-working solutions/brands/advice.
Sam