what can be done to lower 60ft time?

Yeah, get the locker working. Lots there.
Don't put a bigger tire on than needed, they'll slow you down at a certain point.
If it's not a street car, get the front end "loose", i.e. no sway bar, 90-10 shock, you can even work on the bushings to allow for easier lift.
Be careful about putting water in the spare, if you hit something (wall or?) that thing could easily bust the little bolt holding it and be a lethal, flying weapon. I'd stay away from adding weight. Make the car work. Weight will slow you down. Take weight off the front of the car. Sounds like the guy who made those suggestions is an old stock-type racer. (I.E. "rule bender")
Lots to be done. Have fun.