This seems a better place to respond than the other thread....
You noted over there that the gun is canted to the left on this one you just bought used...the USFT guns have a canted grip, the Hunter versions have a straight grip.
Mine is a Hunter but the 4 or 5 USFT versions that I've seen in the flesh had the grip canted to the right, the "right" being from perspective of shooting the gun. Your description makes it sound like maybe the grip is canted to the left of center? I could see that being a possibility for a lefty shooter but haven't personally seen one like that.
The way I understand it, I've always thought that the breech block is where the grip cant comes from. But I just took a look at mine and am wondering if the angle on this plate (just above left side of gauge in this photo) also plays into the cant somehow.
View attachment 348669 Give him a calls during business hours and get a solid answer of what's necessary and perhaps even see if Tim McMurray (MAC1 Airguns) would just sell you a new breech block, one more conducive to a righty so either a Hunter or a "normal" right-canted USFT block.
They're super simple ("Simple Simon"). I'd bet some money that it's just a matter of unbolting and reconfiguring and bolting back up.