The timeline of Gauge conversion define the current boundaries of SR divisions. Except during the bifurcation of PGT division and the formation of SA division in 2007. PGT division currently even after adding on POY-CNV does not have the requisite 600 km track length.
Almost whole of PGT division areas (Jolarpet-Mangalore, Shoranur-Ernakulam) had BG lines in the 1960s.
Gauge...
more... conversion of ERS-QLN MG line and QLN-TVC portion of the VPT-TVC branch line of the MDU division in mid-1970s facilitated the creation of one single BG line across Kerala.
The TVC-CAPE and ERS-ALLP-KYJ lines were planned and added as BG lines. The NCJ-TEN line which was planned in BG instead of MG, enabled the formation of TVC division with MDU division retaining the MG portion (QLN-TSI line).
Most of interior Karnataka (Most of Mysore division) and Tamil Nadu (Most of Trichy and Madurai divisions) were still predominantly MG and Gauge conversion did not commence until the 1990s.
In case of Mangalore, KR was categorically kept outside city limits at Thokur, with undivided SR getting Panambur/NMPT. It may even be allowed to get MAQ CDO but do not see it getting the Mangalore Port.
SR got MAQ uncontested only because HAS-MAQ line was inactive and undergoing gauge conversion when SWR was formed in 2003.