Since there are limited parts for the GX, which vehicle would the modifications be adapted from?
A 4Runner - right?
It is called a 120 Land Cruiser simply for marketing purposes.
The Prado, Surf, 4Runner, FJC and GX are all the same basic architecture.
The Surf aka 4Runner was around long before there was ever a "Land Cruiser Prado" (120) so to say the 4Runner is based on the Prado is not 100% accurate.