I'm looking for a front gas tank crossmember part number or where to find a new or clean used one for a 1999 Suburban k1500

 

You won’t likely find a GM part number for it - it was not something GM considered serviceable and repair parts wouldn’t have been made (barring a recall, which didn’t happen).

If you want an exact match you’ll have to go to a salvage yard.

If you have access to a welder and the means to fabricate a replacement, it can be made from a length of 3” galvanized rigid conduit.

One other option is to get a repair kit from Dorman - they don’t make them specifically for a suburban but it could probably be modified to fit without much trouble.

Dorman Frame Repair Kit

 

The front gas tank crossmember was a servicable part from GM for the 99 Suburban K1500 but I can not find a part number online and nearest GM dealer within a hundred miles of me says he'd have to pull out his microphishe and reader to find me the part number as his new system only goes back to 2000 which is a different crossmember and frame as I have both a 99 and 2000 the 99 has actual crossmembers and my wife's 2000 has the cheap cheesey pipe crossmembers that fill with dirt and salt and rot out. If I had the GM part number I believe I could hunt an oem crossmember down as my nearest dealer said he change a few because the metal gas tanks would colect dirt and salt on the seam lip and rot out the gas tank and the crossmember which mine is not rotted someone hacked mine up to fit a large fuel cell in it and I want to put the 42 galllon tank back in it and get rid of the 80 gallon fuel cell.

 

I apologize for the incorrect info - I’d forgotten that the round crossmembers started with the 2000 models and the 1999 models still used the stamped steel crossmembers.

Not sure where all you’ve looked but I got some promising results by searching here - https://www.gmpartscenter.net/search...tr=Crossmember - so you might be able to find it by entering the VIN on this website.

Once again, Dorman has some crossmembers for pickups which might work with some modifications. I’m more familiar with the truck frames than the suburbans but I know they’re often close in design.