what would I run?
 

stock motored 99+GT with a 100shot?

stock suspension with the addition of SFCs.

It depends on your driving skill. If the question were rephrased to "what would my car be capable of running with a 100 shot?" If you were running a set of 26x8" slicks, N/A the car could run anywhere from a 13.8-14.3...... With the spray you could see low low 13s, possibly a 12 but it would be dependent on a lot of factors like traction, weather, driving skill etc.
SS

on a tire ud probably be able to run 12.5s...

if u set the suspension up u can go even faster I went 13.2 n/a stock with 4.10s and dumps on et streets ... minor weight reduction n et streets

Will the stock rear and axles handle a ET Street?

For a while they would!!
Again depends on how well the car is hooking ,the track conditions and probably your launching RPM's

As for your ET SS is probably pretty close in his estimates!!!
Anywheres from 13:8 to 13:0

My stock rear and axles did manage to stay together when I used ET drag slicks and launched off the limiter at 6200. I only did this about 15 times so I may have got lucky to not break anything. I did see a mildly modified Mach 1 running 17" ET streets break an axle on the starting line last year, it's a crapshoot at best for sure.

I'd ad at least a DR or you'll be fighting all that torque from the 100 shot on stock radials for most of the way down the track. :)