1990 Silverado Stalls

Truck suddenly runs rough, replaced fuel filter and spark plugs. Idles rough and stalls, no pick up. What is the problem and how do I fix it?.

Looks like the key word here is suddenly. Is that before or after the plug change? Loose ignition wires?
Could you have gotten some bad gas?
I would start with easy things to check.
Check for vacuum leak/s.
Insufficient or inconsistent fuel pressure.
Dirty or clogged fuel injectors. Check out the spray pattern.
Then go over the ignition system.
After that the emission controls.
Either buy or goto the library for a trouble shooting and repair manual, worth their weight in gold for shade tree mechanics like me.
What do you suspect? The more info the better the guess that you'll get.

TBI gasket

Check your ignition module under your dist cap. Take it to most parts stores and have them check it for free. EGR, fuel pressure, fuel filter.....Start with the basics.