Is there any website that you can keep you eye on for example n6453?
Certainly, FlightAware will track it for you, but only if you’re the registered owner of the aircraft.
In most cases, I don’t think you need to be the owner of track it. Unless the owner hides it, you can track the plane.
Do you know the significance of that number?
I do! 
The subject aircraft IS blocked J, as the OP knows. He was fishing for a way to track a blocked aircraft.
It’s Nike’s G-4 I’ve been in it before.
Actually, it’s Nike’s Falcon 2000EX. Very nice ride.
The amazing thing about “6453”, the number, not the aircraft, is how Nike has managed to weave it into EVERYTHING they do. Promos, model numbers, etc… You’d think that number made them rich or something… 
So whats the story behind the number?
Look at your phone keys
Its also the last 4 numbers of their customer service #.
I thpought it was their G-4. I sat in it in 2001. they didn’t have a Flacon 2000EX back then
“6453” corresponds with the letters “NIKE” on a phone dial.
Thats it, , thought maybe it was something interesting.
The G-V is now N1KE. Cool huh ?
Yeah- I sat in that one too. The HUD is awesome. Phills golf clubs were in the back (not joking)
Painted in Tiger Woods color scheme.
Gulfstream I-V Nike, now N76EJ.
NO that’s the G-4 that I sat in. The bottom is painted like the bottom of a Nike shoe in the waffle pattern.
the G-5 has yellow and blue on white. take it from me I have been in the airplanes before
lucky! 
Yeah, I kept thinking, “F” isn’t on the 6, I was assuming it might have been several other 4 letter words, as it is, is pretty boring
The number 6453 (NIKE) is part of Nike’s customer service number, part of its store telephone number in NY, San Francisco, Portland, Hawaii and is the last 4 digits of its zip code for its headquaters.
NIKE, Inc.
1 Bowerman Dr.
Beaverton, OR 97005-6453
OR Tel. 503-671-6453
Toll Free 800-344-6543
Fax 503-671-6300