Yes and no, just depends upon what time frame. The only two differences over time were:

The 6cyl carriers were grey iron cast by GMH, whereas the V8 housings (2.78 and 3.08) were nodular iron made by Borg Warner. I think that changed at some stage and GMH started to make the V8 carriers plus the V8 3.08 centre was offered as an option on HK GTS manual and it even had a special tailshaft made for the V8 yoke. BUT, during this timeframe all banjo axles were coarse spline so centres were interchangeable apart from the V8 carrier lower bolts.

The first fine spline axles were used only for the final XU1's and in L34 but very soon after LH introduction the V8 optioned cars got fine spline axles and 6cyl were coarse, only affected Torana though as all V8 Holden were large Salisbury. This changed during LX and HX and after that time 6cyl banjo also became fine spline and the axles remained that way when the banjo morphed into a salisbury, so 6cyl UC and WB plus 6cyl VC-VH were fine spline as well.

Correct. It does seem kind of silly doesn’t it, that some HK-HG that only ever came with a coarse spline banjo were actually heavier and far more powerful (and more importantly “torqueful”) than many HQ that came standard with a Salisbury. For example HK Brougham versus a standard HQ V8 Belmont sedan.

That sounds about right Smitty. Until a certain time in 1967 all red 6 crankshafts were forged until the nodular plant opened then they changed to nodular cast (but kept the forged crankshafts for 161 and 186 S and X engines). I don't think the opening of the nodular iron plant had anything to do with the banjos though. GMH had Borg Warner build all the new V8 banjo centres for HK which were all 2.78 LSD, and they used a nodular case. The 3.08 version was made for the 253 but not really needed as 253 (and 308) were canned from HK very late in design, although some HK were fitted with 3.08 banjo post Monaro and Brougham release (very rare though as it was an optional rear axle). There are notes in the HK Engineering Technical Specs that 2.78 and 3.08 non-LSD would be available once GMH begun manufacturing the centres.