Well HIO Silver is on this one like a hobo on a ham sandwich, but here is my input.

The valve is pushed in by hand on the top of your fuel tank. So you can remove it and reinstall in your new tank.

If you currently have one and plan on reusing it, I'd get a new one so it does not cause possible vapor lock issues if it goes bad.

Going from a valve tank to a none valve tank and not replacing the filler cap with a vented one might cause you some vapor lock type issues also.

You do know you need a different sending unit? Your 19 gal unit will fit, just not read right. Some folks bend the arm...bad idea IMO. Just get a new proper 38 gal sending unit.