3 of 10 added 506 characters in body

Golfscript, ~1e+1000595

9{.*}20*

Runs in 8 seconds:

$ time echo "9{.*}20*" | ruby golfscript.rb  > HUGE

real    0m8.025s
user    0m7.947s
sys     0m0.075s
$ wc HUGE
       1       1 1000597 HUGE

$ head -c 80 HUGE
62169567991317960591005372494582745002820021564023336307697854677255557017989252
$ tail -c 80 HUGE
5015814850582980958687124312295507101846975422626734412975476315837370193674241

The bottleneck of this answer is computing speed. The 20 can be changed to 9999, but 21 takes 3x as long as 20, 22 takes 2x as long as 21, etc... so 9999 would never finish within an hour. I'll see how far I can bump this up until it does finish in just under an hour, though.