Just out of curiosity's sake, how can you tell it won't fit?
Because on a real G80-1800 there is some space in-between groups of keys, space that I can not see here.
On this PCB you can see an unbroken row of nine one-unit keys on the bottom row. On a real G80-1800, that row is broken: the cursor keys are forward and with space around to the main area and to the numeric keypad. There is also space between Return and the numeric keypad on a G80-1800. There is also 1/4u space between Esc and F1 and between each function-key group.
BTW, I think you would need a Teensy++ if you are going to support all keys. A regular Teensy doesn't have as many I/O lines as this keyboard has header pins.
I think this keyboard could be great cheap PCB to cut up into a custom 70% or whatever. I am tempted to buy one just for that.