The difference in trays is one is for the 340, possibly an OE tray since the holes are not slotted. Or an early MP tray which is really the same thing.
The slotted holds one is for ether 340 or 360. It is probably a MP tray.
X2 I do have have a stock 340 tray, and a new MP one in the box, if it really matters I can take a picture of the two.
The slotted holes are to make it fit all small blocks.
