Are 3.90's worth it
 

HOw much time could i expect to gain in the 1/8th mile with 3.90 gearset as opposed to stock 3.42 assuming I had drag radials and could at least get a 1.8 60ft.

you need to concentrate on getting the 60' down lower than 1.8 60' before you need more gear. i wouldnt put an aftermarket gear set on a t56 car with stock 10 bolt.

Probably nothing.