I have a plastic LS1 tank that I am putting in my 1989 Camaro along with a LS1 and T56. The stock fuel level sending unit reads 33-240 ohm (empty-full)...

Here is my question to you....
My new fuel gauge dose not read 33-240, it's 240-33 ohm. I was going to bend the float arm so that it faces the other way... Thus correcting the problem.

The fuel gauge would be accurate, but I thought the fuel level data was sent to the PCM for EVAP calculations... wont this throw off the EVAP system? This needs to be a smog legal swap.

 

Yes, it will throw off the PCM for its emissions functions.

The options are swapping in a 4th gen gauge cluster, or putting in a programmable fuel gauge (I did the latter in my LS1/T56 swap in which I used a 4th gen LS1 plastic tank). Since you said "new fuel gauge", sounds like you should have gotten a programmable.

 

Mount the gauge upside down. LOL!

 

Guess I will have to pay another $100 to convert to 0-90 ohms.

1 last question. I have a 1998 style LS1, but I was tld I will still need the platic tank. In 1998 a metal tank was still used. Is there any diff in the EVAP between 98 and 99-02??

 

If you've got a '98 LS1 engine and emissions system, and a '98 LS1 tank, whoever told you that you need a plastic tank is simply dead wrong.

Leave the sender alone and use a programmable fuel level gauge, like you said you are going to do in the thread about plastic tanks.