Should fit under a Canadian poncho.
https://www.kijiji.ca/v-classic-cars/calgary/impala-x-frame/1328379982?enableSearchNavigationFlag=true
Good frame and great price! $200.00! I already have a good spare.
This is where they rot out the fastest (back mount corners):
Prince Edward Island'64 Parisienne CS "barn find" - last on the road in '86 ... Owner Protection Plan booklet, original paint, original near-mint aqua interior, original aqua GM floor mats, original 283, factory posi, and original rust.