The BBD gets dissed a lot ... I suspect that it's really somewhat better than those that tell you it's the worst carburetor ever. Certainly it has some specific issues, like the plugged idle tubes (article on fixing that linked above). In principle, it's a good design, with the same metering rod design as the well-regarded Carter YF that precedes it, and the famous Rochester Quadrajet. If you rebuild it and clean out the idle tubes and give it clean fuel, it should work fine as long as it has not been mangled by the PO.
That said, I'm an enthusiastic supporter of fuel injection if you want to take on such a project. I don't know that I'd recommend the Howell kit, unless you want a CARB number to be emissions compliant in California or where ever. If you are a DIY-er with some electronics and computer chops, look into the Megasquirt board, or if you want a turnkey system, Bill Hamilton sells complete systems that he custom tunes to your engine. The Howell product is a fuel-only implementation of the GM throttle body injection, and as such will be tuned to a broad array of 258 applications. You can do better - adding spark control, and tuning specific to your engine.
