I wouldn't call the II numbers indicative of a top. Almost by definition market tops are associated with high levels of bullishness. However, there is a cause and affect issue here and it doesn't necessarily mean that high II causes a top.
Lets not forget that for 3 years many pension funds as well as foreign funds and insurance companies have been pulling dollars out of the US. Most recently in the run-up into the war when we almost hit new lows before bottoming. That means that even with high levels of bullishness there is still an enormous amount of money that is finding its way back into the markets.
If you want to see find chinks in the armor, we have to start seeing junk bonds start to break down. However, they aren't. They continue to outperform the market and new issuances are occurring at record levels. CPN's 3.3B deal this past month is remarkable considering their debt was trading at 25% yields a year ago and the stock was at $1 and change. If companies get to rollover their debt then everyone is happy at least for awhile. People stay employed, capex gets reinstated, etc. Don't expect a crash anytime soon.