When the VB was released, it was a revelation, not just for Holden, but for the Australian motor industry generally. Dynamically, it was clearly superior to just about any Jap car available here at the time. (think Corona's, Sigma's, for example - very ordinary cars, but typical of what was being served to Australians in 1978). It might not have had the gimmicks and features of the Japs, but it was a better car in the things that mattered, like handling, comfort and primary safety. It had seen a basic German design, which suffered chronic structual weakness when being tested during Commodore developent, strengthened and modified to ensure long term durability in our conditions. As pointed out already, it's greatest weakness was the engines. The sixes were way past their "use-by" date and it was only Holden's poor financial position in the mid to late 70's that prevented them being supplied with more modern engines. The V8's were a bit younger and still had a fair bit of life left in them at that stage. The transmissions were also out of date - by the late 70's, three speed auto's and four speed manuals were becoming obsolete, yet Holden soldiered on with both for another ten years before they were completely dumped. Five speed manuals became optional after only a few years, but that was the issue - they remained an option, not standard, until the VN.
I'm with the OP regarding his proposed upgrade. If it was legal for him to do it, I would have turfed the old L6 and standard trans for a V6 as well.
I can clearly remember the release of the VB. It was the biggest news from Holden since the HQ, but probably much more significant, because it showed a whole new direction for the Company with future models.