whats the diff

[HK1837]

Was Belmont ever v8 though?

Yes plenty ok HK Belmonts optioned with a 307 and plenty of HT-HQ V8 Belmont models. HJ to HX Belmonts optioned with a V8 are probably less common as Belmont was confined to sedan and wagon at that time.

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They definitely had different quality of bench seat and from memory Belmont never had a radio as standard.

Hardly any Holden from HK to HX (Belmont era) had a radio as standard. I can't remember the specifics but maybe only HX LE? Very few would even have been assembly plant fitment even if optioned.