Everything is different.
The frame tubing is traditional round tubing. It uses 990 U-brakes. It has a 19.5" top tube. There is nothing similar at all in the looks of both bikes.
The 300TA came as a complete bike only, and the regular T/A's came as frame and fork set only.
The ONLY thing that these 2 had in common was that they rode excellent!
The 990 U-brakes were a major upgrade in the braking department for sure!
The 300TA is an Excellent ride, and is my all-time favorite 20" bikes to pedal around on.
the 300TA did have a major flaw though.... the brake cable is routed through a hole that was on the bottom of the downtube. That hole was a starting point for a nasty crack in the tubing if you like to jump alot!