It's been a while since I typed one of these up... Here we go... (I'm assuming you're dealing with the '94+ composite headlights that take 9005/9006 bulbs based on your avatar picture)
Headlight assemblies:
Are you wanting to stay with the OEM style diffused lenses, or would you be interested in going to a non-diffused clear lens? If the former, I'd stick with OEM. They're still available new but they're expensive, think $150+ per side. If the latter, I'd recommend either the Anzo 111004 (plastic lenses) or the Spyder HD-YD-CCK88-C (glass lenses). I have the Anzos in both of my '97s and I'm very happy with them. Either of these can be had for around $100 per set.
Anzo 111004:
https://www.amazon.com/gp/product/B0015PPZMC
Spyder HD-YD-CCK88-C:
https://www.amazon.com/Spyder-Auto-Chrome-Crystal-Headlight/dp/B004WMF8SG
Wiring upgrade:
This is one of the most commonly overlooked upgrades to the headlights in these trucks. Upgrading the headlight wiring harness to a larger gauge wire with relays that pull power straight from the battery will gain you over a full volt at the headlight plugs, which equates to much brighter output. We have a user here (
@5vortec7) who makes these harnesses complete with 4-Hi modification, which means your low beams will stay on as well when you engage your high beams. This is an absolute must if you want more brightness from halogen bulbs IMO. Here's the link to his thread where he sells these.
https://www.gmt400.com/threads/hd-headlight-harnesses-w-4-high-mod.45669/
Bulbs:
The absolute best, brightest 9005/9006 halogen bulbs on the market are Philips X-tremeVision. Unfortunately most stores (at least in my area) don't carry them. You'll probably have to order them from someplace like Amazon. Here's some links.
Philips X-tremeVision 9005:
https://www.amazon.com/Philips-X-tremeVision-Upgrade-Headlight-Vision/dp/B01C5QY7DW
Philips X-tremeVision 9006:
https://www.amazon.com/Philips-X-tremeVision-Upgraded-Headlight-Vision/dp/B00U1OLM1Q
If you want something that's more readily available, Sylvania XtraVisions are in the same ballpark as far as output and are stocked in most parts stores and Wal-Mart.
Sylvania XtraVision 9005:
https://www.amazon.com/SYLVANIA-XtraVision-Halogen-Headlight-Contains/dp/B0031HI0HY
Sylvania XtraVision 9006:
https://www.amazon.com/SYLVANIA-XtraVision-Halogen-Headlight-Contains/dp/B0031HEIDY
Whatever you do, stay away from halogen bulbs with a blue coating on the lens (like Sylvania SilverStars) as that coating actually robs you of light output. You want clear glass. The Philips X-tremeVisions are the one exception I'm aware of. They have a tiny bit of blue added to the glass in a specific spot just to keep the bulbs within spec. Without it, they'd be too bright for 9005/9006 specs.