My truck won't stay running
 

1990 Ford ranger, needed a tune up I changed spark plugs and wires gapping spark plug at .44 now it won't stay started...

Welcome to the forum

No real reason comes to mind from just changing the spark plugs

1990 Ranger would have 2.3l SOHC Lima engine with dual Coil Packs and 8 spark plugs, if would use a Crank sensor with ICM(ignition control module) for spark control

I assume its starts OK, but how long does it run at idle?
"Won't stay running" is a vague time period, lol
Can you drive it and it stalls, or just stalls soon after startup

Could you have knocked off a vacuum hose?
That can stall an engine