Winny used the Chevy chassis in the 37' Elandan models.
Here's one: 1988 WINNEBAGO ELANDAN for sale in ERWIN, Tennessee on The Big Lot!
About the only drivetrain change might have been rear axle ratios.
GM (and Ford) provided fairly generic chassis. The various coach builders just drop their coach on those chassis. As long as it fits and MAYBE it leaves the factory without already being over the gross weight rating, then they are happy. Those longer coaches simply got a tag axle stuffed under them to handle the extra weight and length.
Any additional drivetrain and suspension upgrades are left to the buyer.