HK GTS327 and HT-HG GTS350 manual are the same and hard to find. I think the only other place you find them is HK GTS and possibly HT V8 manual GTS. I can’t recall for certain if there are others, I know HT-HG GTS are different (same springs but different front eye), not sure about HT V8 auto GTS.

From memory yes, identical suspension to HK GTS327 (and same rear springs as HK GTS) except for raised upper control arm locations and slightly wider front track. It was the rest of HT and HG GTS, V8 GTS and auto GTS350 that started to go backwards (in terms of suspension performance), but I can’t remember exactly which ones changed and when. Although I do remember all auto GTS350 and all HT-HG GTS use different rear springs. It is the HT-HG V8 GTS that I cannot recall exactly.

I just checked and HT V8 GTS manual also had the HK GTS rear springs, and HT GTS also had the same springs except they used the large front spring eye for a larger bush. So that means:

HK GTS
HK GTS327
HT V8 GTS manual
HT GTS350 manual
HG GTS350 manual

had the same rear springs.

Finding them today is near impossible, one or two of the leaves are unique. Last pair I saw sold for well over $2000. I have been lucky enough to get hold of 4 sets for the two GTS327's and the two HK GTS's that my mate and I have between us.

What's is the point you are after benny, just to be original or you are looking at it from the handling side of things.
I had ute springs in the back of my HG Premier.

I had to buy a whole HK GTS to get the last pair, but luckily it came with a whole heap of other goodies as well. It was one rusty POS Flintstone car that would have been impossible to repair.