If I recall correctly, you had both trucks, complete, at the beginning of the project? Which mount parts are still in your possession? There are 'legs' that bolt to the engine blocks and there are the mounts themselves, the rubber isolator with the steel plates on each side for attaching between the block legs and the frame pad.

Do you still have the rubber mount from the diesel? The diesel and gas rubber mounts do differ, but at least with my conversion, they both bolted to the frame in the same manner. I'd think you would just need to use the mount from the diesel, not from the gas engine.

The frame mount pad may (should?) be the same between the gas and diesel frames - someone else would have to verify this for the C223 and 1989 chassis (it is for the 4JB1/4ZE1 in the 1988 chassis, anyway).

Since the part you're speaking of is removeable, unbolt the gas mounts and use the diesel mounts in their place if you can.