NEW YORK (Standard&Poor's CreditWire) Jan. 26, 1999 -- Standard&Poor's assigned its single-`A'-minus rating to Illinois Development Finance Authority's $96.36 million hospital revenue bonds series 1999 dated Jan. 1, 1999 due Nov. 15, 2029, issued for Adventist Health System Sunbelt. Standard&Poor's also assigned its triple-'BBB'-plus rating to Illinois Development Finance Authority's $75 million tax-exempt subordinate capital securities series A dated Feb. 11, 1999 due Nov. 15, 2038, issued for Adventist Health System Capital Trust I. The bonds are scheduled to sell Feb. 8, 1999. Both issues were originally rated and scheduled to sell in 1998, but state approvals permitting the acquisition of LaGrange Hospital in Chicago were delayed. The single-`A'-minus rating reflects solid credit characteristics