I'd agree that assuming the OP can get to 4w/kg ( "bare min pro level" for a cat1 / regional pro cyclist) assumes he can up his FTP from 257w to 320w which means he'd have to be really green OR lose 33lb of
fat@257w......or something in between that. 320w of trained, sustainable power is a university level athlete, and the OP would know they are a pretty decent athlete off the bat.
To do that just on weight: He'd have to start at 180lb and get down to 147lb @6% fat ( athlete training fat %, sub4 or 5% is not a ). This means he'd be starting at about 25% body fat or would need to atrophy the equivalent amount of upper body muscle.
More sensible for a 19yr old, he's probably 13% fat. He can probably get down to 77kg lean, so would need a 310w FTP for that 'magic' 4w/kg number.... this again is only realistic if he's pretty green.
NOT trying to kill any dreams.... and that number doesn't really matter..... Just highlighting some aggressive math by everyone in the thread. Starting FTP and weight give you wildly different rooms for improvement in a vacuum without more info.
OP wanted to know what ball park he's playing in. I'd say he can be in the mix on a flat surface and might fare better with some light hills. If he responds to training well, is pretty green, has room to hang with the big dogs - probably not a climber or TT specialist though, would need a lot of "punch" to stay with the group, and would need to be able to hold near this power for longer than an FTP test ("Fat max" close to FTP).