The Pre-Production verson of the Boba Fett costume was shown in various studio shots before the actual movies were released. There were many differences with this suit as compared to the two original movie suits.
A great example of a Legion approved Pre-Pro Fett costume can be found in the Florida Garrison:
The Pre-Pro flight suit is more like the ESB suit in color. Its very form fitting and a blue/gray color.
The Pre-Pro flight suit is interesting in that it has two different color guantlets. The right one is the maroon color that the RoTJ suit uses while the left one is a bright yellow color. The flame thrower attachment on the left guantlet is more like the ESB one… thin metal poles stick off the outside.
The girth belt is the same as the ESB Fett: a dark brown, 14 strand mohair horse girth.
The gloves are another distinct difference in the Pre-Pro suit. They're a two toned brown/tan color with Army patches sewn on the hand backs.
The Pre-Pro cape is the same, OD green, army half shelter as the RoTJ version.
The rocket pack is similar to, if not the same as the RoTJ multi-colored pack.
Very similar to the RoTJ armor in color. Less weathered than either movie version.