3/4 ton drum brake ????

[90suburban]

Hi all first time posting looking for help! What I have is a 90 GMC suburban R2500 and I am trying to replace the rear brake shoes. It has the 14 bolt 10.5 FF with the 13in drums. The issue is that it had no adjustment hole on the backing plate so I can not loosen up the shoes to pull the drums off!! I can not get the drum past the ridge on the back of the drum from ware and I can not loosen them up because there is no adjustment access hole! Any help and suggestions would be great.