Virg,
The sending unit in your truck should be a 30 ohm unit, which is correct for your gauge and for all year rigs on either side of your for quite awhile.
Although I'm not sure on this, I think the float/sender for your rig is common with most previous years...with the exception that the earlier ones might not have had a suction tube coming out the top. This might be why the differentiate between '54 and older styles.
If the float was installed wrong and is hanging on the tank side it could cause problems. Generally speaking, if the new sender isn't bum from the factory, it should work. There are procedures to test the gauge to see if it is the culprit or the sending unit is at fault.
I think the gentlemen who posted above linked some of these troubleshooting techniques. Good luck.
Stuart
