Penrite is 100% Australian owned & managed. The oils are 'made & blended' here in QLD & VIC but the best base stocks are sourced from various places. No oil company will reveal where their base stocks come from, but Australian companies have been making a concerted effort to source their stock from the USA, Russia & Sth East Asia. We rely on Middle East for close to 40% but there has been huge increase in production in Indonesia & surrounding areas. With the proximity to Aust, this is the most likely future market. Remember all oil companies do this & Penrite HPR is as Australian as you can find, but most importantly, was developed for Australian conditions. I hope this helps explain your question.

It's hard to judge the age of a Winsor seeing as they've been around so long, but at a guess it's had a fair bit of work done to have a solid cam and (at a guess, maybe edelbrock heads).

If the previous owner ran a 40w oil, then go with it. I doubt they would have used a full synthetic as they show up oil leaks in older motors. Probably best to ask the previous owner what type (mineral or synthetic). If you find its using a bit more oil than you like you could shift up to a 50w oil, which for a worked motor (and I assume you have a 750 or 850 carburettor or a blower on top?) which run hotter, would be fine.

Cheers

Your engine your money I know it's not cheap Mobil1 5w50 for the old style Windsor and 0w40 for the later engine I only use Mobil1 in my own