Mark is right, and you've set the stage for problems when you mentioned that you cannot afford, or don't want to buy new accessories for the Vortec when your period correct parts were fine. If you're wanting to keep the Buick somewhat "original", what some call a "resto-mod" or "resto-rod" for older stuff, then rebuilding your Buick engine is the way to go. If you don't care, and are looking to improve your driveability/reliability, then another option is a total takeout package from a later model vehicle, engine, tranny, ecu, and engine wiring harness in a package pulled from an operating vehicle. There is a growing group of businesses catering to this approach, offering varying warranty/guarantees on what they sell. One out west is Pacific Fabrication, which seems to have some very reasonable package pricing - Take Out Engine Packages - Engine Packages - Engines - Engine & Transmission - Products