I have a 94 Corsica with a bad fuel gauge. I think it's the sending unit/float I found a unit on line $17.00, but they say there are two that might fit it. One is 90 ohms and one is up to 400 ohms. The Chevy dealer says there is only one listed in their book, $163.00, but they don't know how many ohms. Is there a way to tell this.