[gmc684x4]

Yes there is a difference the light has smaller range it eorks in and the guage sending unit works over a broader range

Do you have acess to a coolant pressure tester ?
Many parts stores may do loan a tool on these

You pressure up the system and leave it for awhile see if it drops in pressure over time
This will confirm any leaks in the system

Higher flow water pump and 6 blade fan or fan cutch fan can help
Clutch fan needs to be proper rotation for water pump
Example 88 98 the water pump pully goes in reverse direction

Sender could be a bit out of range as well