Im here.. Im not quite at 1400 yet.. it was 1300 rwhp at 11 lbs pump gas but im sure at 12 it would be 1400. Turbos are nice 1 lb boost equaled over 100rwhp, and my engine should take 15 lbs quite easy on pump swill.
The big reason to go a single over a twin turbo is simplicity and cost!
With twins you need
2- Wastegates
2- Blow of vavles
2- turbos
With a nice single you can get away with 1 of everything (depending on displacement, I have to install a 2nd WG to bring it down to 5 lbs). The cold side plumbing is more on a twin and on a single there is more on the hot side.
If you size your turbo's correctly they can be equally responsive either single or twins. Also cam profiles are a witch doctors forumla!

You can stock block a turbo engine but don't expect it to live over 1000hp for too long. I went to a KB street 440 block for the simple fact its the best block out there and they can fix it if you ever window it. I run nothing wow for heads (victor 440s), walbros and a megasquirt for my EFI.
jyrki is definately right about starting to look at other things in the car once you make the power!
Ive had to get rid of my cal tracs and small tires because really 1.57 60 foots really suck. Also petaling the car all the way down the track is fun but doesn't result in anything more then a 9.1 or so

.
So a backhalf is going in unfortunately because the tracks here suck.. and now a hammock will take place of the back seat! damn it! And the 727 handled the power except it never hooked so that tranny is doomed. It handled 1000 HP hooked but I dont think much more then that. Hence now i'm looking at a powerglide... which is kind of going to suck on the street now with only 2 speeds. The 8 3/4 all back braced, etc etc etc would possibly hold the power but a 9" now is in its place. Also need 25.5 now for the cage.. etc etc etc! So yes the list of things to do piles up.
Junkyard turbos are nice, but if your really cheap you can buy master power turbos so why would you screw around with used stuff? Ive learned you spend the money twice buying used shit, unless you know where it came from.
Another thing, pump gas E85 in the states is the ticket... if you class that as pump gas! I should be able to turn mine up to 25 lbs boost on that stuff.
Anywho if your thinking of singles stock block follow TT440's lead hes got something going that for sure.