** Mental healthcare provider LifeStance Health's LFST.O shares up 5.9% at $7.70 before the bell as it's poised to join S&P SmallCap 600 index .SPCY later this week
** LFST to replace Golden Entertainment GDEN.O in SPCY effective Fri, May 1, S&P Dow Jones Indices said late Mon
** Casino operator GDEN being acquired by its CEO Blake Sartini and Vici Properties VICI.N in $1.16 bln deal expected to close on or around Apr 30
** Stephens analyst Melissa Roberts said she expects passive funds will need to buy 26 mln LFST shares, implying about 12 days of purchasing demand
** Historical performance of S&P 600 Health Care .SPSMCA new adds implies LFST should outperform from announce to add with the bulk of outperformance on Apr 28, Roberts said
** Over the last 10 years, new adds outperformed the SPSMCA by average 8.2% on the day after the announcement and by 8.9% from announce to add, she said
** Scottsdale, Arizona-based LFST has ~387.8 mln shares outstanding for ~$2.8 bln market cap
** Private equity firm TPG TPG.O is largest LFST holder with ~140 mln shares, per LSEG
** Through Mon, LFST's stock up 3% YTD including 14% gain this month
** Avg rating of 11 analysts is "buy"; median PT $10
(Lance Tupper is a Reuters market analyst. The views expressed are his own)
((lance.tupper@tr.com 1-646-279-6380))