Yeah, you HAVE to get those bolts out otherwise the pump'll leak. I'm sure that buick small block is the same as my SBC which means 4 bolts hold the pump in, 2 on either side of the pump on either side of the gasket. You're gonna have to invest in some extractors, or drill them out and retap or helicoil. I'd try to extract them first, make sure you soak 'em in PB Blast. That shit's bad ass, isn't it?