I refurbished the grill on my ‘37 about 7 years ago. As I recall, have photos somewhere, the grill sides were held in place with a type of cage nuts. Several were broken off apparently from collision damage. I recall this because after straightening the grill bars and polishing all the related parts then reinstalling it, I had to use a different type of “clip on” cage nut. I think I found them at Fastenal. The real joy came in the wrestling match to reinstall the grill assembly. Reaching up from the bottom to bolt in the upper bolts was not possible with my arm length. Son came over and his longer arms made it a quick end to the misery. I also had to use short lengths of twine to pull and adjust to grill to seat or align in the opening while securing it in place with the bolts.
SP Harrison–sent you a PM