Does anyone have pics or drawings of the interior arrangement of 40mm (Bofors) ammo lockers on PT boats?

I don't have any pictures or drawings, but I can tell you this. The 40mm ammo storage consisted of four horizontal racks, each capable of holding four, four round clips of 40mm shells. The rack was solid on three sides, and had a roll up canvas cover protecting the ammo on the weapon side for easy access by the loaders. Approximately 5'wide, 4 1/2' tall, and 1 1/2' deep in full size. Viewed from the side, the rounds lay in the racks at a 45 degree angle, with the projectile part facing down and forward.

Thanks!! That's exactly what I needed to know!

Depends on which boat during what time period.

Wouldn't any boat with a 40mm Bofors have the same design (standard) ammo locker?

No, especially among the first boats being fitted. Initial stowage included deck mounted ready service lockers similar to those for the 20mm and angle iron racks holding the metal transport cases. The vertical lockers were standardized much later.