I have a '98 k3500 fwd and want to add an elect. trans gauge to my oh/console any help would be appreciated, like where to tap into the (4L80-E) trans with the gauge sender.....

 

For the sender to be most accurate you can drill and tap the pan. Easiest thing to do though is use the pressure port on the driver's side above the electronics...it's 1/8" NPT and the sender should thread right in. It's not as accurate as in the pan, but it's easy.