power steering pump seal blowing out....5 times now

Steering gearboxes are interchangeable '62-'72 A- and B-body. The reason the '76 doesn't interchange is that '73+ A (etc.) bodies got the larger pitman shaft. A P/S pump/box mismatch is also not the problem. Sounds like poor-quality and/or incorrect seals are being installed. AutoZone sells garbage; they're fine for buying cheap oil and stuff, but not actual working parts that you actually want to have work. Get with Steer & Gear or Firm Feel for good quality, correct repair parts.