From memory the VZ Monaro and SSZs had slightly better brakes than standard that would probably do for what you want with some better pads and not be very dear secondhand.
For suspension I’d definitely contact the guys at Protek (Bridgestone) in Oakleigh. The owner (Black Diamond) and most of the guys who work there are on this forum and will give you absolutely no BS advice and do great prices, especially if you mention you are on the forum. BD doesn't get on here much now, so best to ring them. (03) 9569 0834
Head/cam is something to talk to Chev about – can’t really help you there but FWIW Chev is offering 15% discount on cam work over $3k for subscribers to his website if commenced before the end of March, so good time to be looking!
Chev can also adjust your trans so it no longer thumps into 2nd. Apart from that I’d leave it if/until it starts playing up and then look at a strengthening rebuild.