1995 Buick 3800 starts up runs about a minute shuts off.

if you put an engine in a car that has been sitting for who knows how long,then first thing you should have removed the fuel tank and got the old gas/water/crap out of it and cleaned it out.

Here is where I would start testing > Find a fuel pressure test gauge (parts store rental) and check fuel pressure at schrader valve .. Old gas is certainly not helping! .. May have water in gas, using the fuel test gauge pressure release hose, you can take a sample to check for water in fuel - in a clean clear container... Remove fuel filter and check it for water as well... 'IF' fuel pressure is ok, strongly suspect water in gas tank!