thanks - first test will be a jump wire from the sender base to a good ground. if that doesn't work, I am inclined to try the old sender (have no idea if it works as car wasn't running when i got it) or a new TS58. Third test will be to remove the inline resistor on red/black wire on back of gauge to see what effect if any that has (given that it''s old, it's suspect).
Any other thoughts?