best conversion from divx when its 608x320

[substance]

im trying to covert divx movies to svcd, and when you get the divx files with the 608x320 resolution (with the letterbox cut) it doesnt come out right after conversion using 480x480, whats the best for me to set it for so its not distorted when i play the file as an svcd?

[Truman]

I f you use TMPG, try source aspect ratio 1:1(VGA), video arrange method "full screen(keep aspect ratio)"