Run what the manufacturer suggests.
sounds right to me
It's a longstanding debate and you'll get a number of answers, ranging from 87-93. Conventional wisdom says run 87 unless you get pinging. There are plenty of high mileage 2V 900 engines out there that have been runnin' 87 their whole life without nary a problem. OTOH, there are plenty of strong opinions that insist that you HAVE to run 89.
Personally, I ran 87 in my monsters until I installed hi-comps. Now it drinks 91.