I would do the box now, it is in your budget, and it really really adds to the "feel" of the car. search "thirdgen steering box" and "Brian Lewis"
I did the g/s mod squatting in the fenderwells, with the spindle and lower control arm between my legs, headers on engine in. Only took off the upper arm. It took 3 hours total, from on the wheels to on the wheels.
The only tricky part is printing the template to the right size. The x's for the original bolt holes hafa line up with the original bolts. Use pozzi's template, not guldstrand's. People have had trouble with guldstrands even tho they are supposed to be the same. Best way on the template is to measure the distance between the bolts, then take it to your office copier, and play with the zoom till you get the right distance.
Before you drill the second hole, measure CAREFULLY, or even put the crossbar in place to ensure the 2 new bolts will actually go thru both holes.
Then cut the ears off with a sawzall, again, you can do this from under the wheelwell. Might want to take the plug wires out of the way.
This simple lil thing makes a HUGE difference in how the car handles.
Tubular a-arms are bling. They really don't do anything but look good. They add a lil camber, but you don't need more than 4 degrees and you can get that with shims. Tubular arms DO NOT change the basic geometry of the suspension.
Study on the springs, both the rate and the ride ht. there's simply too many choices. The racers like stiff springs, I get along real well with near stock spring rates and a big swaybar. My front fender lip is 23.5" off the ground, and my hooker comp headers rarely strike pavement.