cac_sabre:
I used to live right next to Goroka airstrip as a kid when GSA was operating. I doubt if there are any colour photos available to confirm this but, from memory the chequered rudders were black (or very dark green) checks superimposed on the silver colour of the fuselage (fabric or metal).
GSA operated Austers, Norsemans and Junkers 52s, as well as the Lockheed Lodestar pictured. According to James Sinclair's book "Sepik Pilot", the Lodestar was leased from Fawcett Aviation when Gibbes was hoping to get an airline licence to operate a regular service from Port Moresby and Sydney via Cairns and Brisbane. The licence request was refused by DCA on the grounds that it would compete with the established airlines already operating the route. GSA handed back the Lodestar in 1953. According to Sinclair the Lodestar "...was a financial and operational embarrassment from the start. It was expensive to operate, unserviceable for long periods, and unsuited to the type of internal operations the Company conducted; ..."
If you want to get the best information on the operation of GSA, I would suggest you get a hold of James Sinclair's excellent book "Sepik Pilot", published in 1971 by Lansdowne Press SBN 7018 0323 1, which details the history of Bobby Gibbes and GSA. Unfortunately, I doubt this book would still be in production but may be found in a library somewhere.
From James' book, in addition to the Lodestar, the aircraft operated by GSA included (all VH registrations):
Austers: KSD, KSQ, KSS,KSU, KST
Norsemans: ASN, ASS, ASR, BLM, BNE, BNL, BNT, BHG, GSA
Ju 52s: BUV, BUU, BUW
Hope that helps.