Going from 120W or even 170W FTP to over 300 is nothing short of epic.
It's book-worthy material, no less.
Assuming you will get to 170lbs or perhaps 160lbs (72kg) it will be around 4W/kg which falls into Cat 2 category Just How Good Are These Guys? | CyclingTips
I'm not sure how accurate those numbers / categories are but looking at strava it appears that there's very very few who can do 4W/kg or more and all of them have years and years of training.