Bob, They look like they are the same size but I think the problem comes in in the cooling department. The 318 is a 2 cylinder and has what looks like a oil cooler right behind the vented area.
Here is a shoot of a 318 panel.
The 300 is a single cylinder tractor with the vents in the front.
I don't want to say they will not work but I believe the function out ways the fit. I don't want you to over heat your 318 and burn it up..

Here is a shoot of a 318 panel.

The 300 is a single cylinder tractor with the vents in the front.


I don't want to say they will not work but I believe the function out ways the fit. I don't want you to over heat your 318 and burn it up..