I notice that the engine is listed as a 2850 that makes the GTR a LC and not necessarily a LJ though I do conceed that all previously homologated parts could have been used, however that would not make them standard production.
From my information Holden did make provission for a special 2850 engine for this purpose but the WW carbie set up would not fit the LJ without linkage modification and exhaust changes. that would not be standard GTR production.
The 202 single barrel carbie 1 5/32 was no match for the 173S engine of the LC GTR.
Mike