216-235-261 Chevy, 'PG' is power glide. The bottom plate mates perfectly with a 216 exhaust, or 235 up til '53, after '53 you will need to fabricate (or buy) a heat plate for the bottom of the intake and run exhaust heat from Fenton headers or pipe in hot water for the carbs to run right. Better pictures below...any chance you are selling?
What is the diameter of the intake ports? How far apart are the carb studs? That is the distance between the mounting stud centers of one of the carbs. These measurements will tell if it is for a 216 / early 235, or for a later 235, and what type of carbs it is designed for. Yeah, I've been looking for one, for awhile.