Highest Chart positions according to the best resources I have available.
The US numbers are from Billboard. The UK numbers are from the current official chart site.
It should be noted that both countries had multiple charts at the time which could be considered official, for example in the US they used both Billboard and Cashbox as major charts.
Positions from other countries are from the best sources I could find online and so should not be considered definitive.

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*Note: 'Welcome 2 My Nightmares' chart positions are confused by the fact the album first came out in the 'Classic Rock Fan Pack' which wasn't eligible for the charts. Most UK and a large number of European and US people got the album this way, so when it was released to retail most fans already had it, obviously effecting sales positions.

**Note: By the time 'Road' was released the main UK and US charts (and possibly other countries) included music steaming in their calculations for placings and not just real actual sales. This meant that while in the US 'Road' only entered the chart at #160, in actual sales it was much higher at #11. The difference being the huge number of streams (and in the US, radio plays) pop records could get, sometimes using "server farms" to stream a song thousands of times a minute to inflate the numbers and get a hogher position.
There was also a problem in the US with the distribution of the physical albums to retailers like Amazon (the single biggest retailer in the world) with many reports of pre-orders being delayed, sometimes up to several weeks, and the album being 'out of stock' the day of release, which certainly didn't help the albums chart positions.

Some important facts about album certification status

1) What the public often doesn't realize is that US Platinum albums (sales of over 1 million units) only came into being in 1976! Prior to 1976, there was only gold certification (sales of over 500,000 units). 'Billion Dollar Babies' DID, in fact, sell more than a million copies in 1973, but there was no platinum certification prior to 1976. 'Welcome to My Nightmare' DID, in fact, sell more than a million copies in 1975. In fact, 'Welcome To My Nightmare' sold more than 1,500,000 copies in 1975 but there was no platinum certification prior to 1976. 'Killer' and 'Alive Cooper's Greatest Hits' had also sold over 1 million copies in 1972 and 1974 respectively. So, Alice had at least four albums that had sold over million copies each but they were not certified platinum because they were released prior to 1976.

2) In 1986, Warner Brothers finally got around to retroactively certifying million-selling albums that had done so prior to 1976. So, that's why those above-mentioned albums were finally certified platinum in 1986. Notice that Warner Brothers waited ten years to retroactively do so. So many AC albums did NOT take a long time to sell over a million copies. They just were released prior to 1976! Furthermore, other albums like 'School's Out' sold over a million copies way before 1986 but had to be retroactively certified after 1986 too.
(Susie (Glamprincess), August 2005)