The 2nd gen 250R (83/84) fork tubes will work. If you use the damping rods from the 250R forks, you'll get a little bit more travel. Use the 350X lowers so that your axle and brakes mount the same way, but you can use all the other guts from the 250R forks.
I'll vouch for shortline's straightening service. I sent him my 350X forks and my brothers 3rd gen 250R forks. He straightened them out perfectly.
- Frank
1984 200ES Big Red
1985 350X (x2)
1986 350X
1986 250SX
1984 Auto-X
1984 ATC70
1985 ATC70