Design Evolution

"So far I found two different engine mount bolt patterns used in three different ways.

1. 4 bolt engine mount bolt pattern w. all...four bolts in usage
2. 4 bolt engine mount bolt pattern w. only three bolts in usage
3. 2 bolt engine mount bolt pattern w.........two bolts in usage (truck ??)"

1958-1964 Mounting Pad

http://hotrodders.com/gallery/data/500/422FEmotormountpad_58-64.bmp

1965- Mounting Pad

http://hotrodders.com/gallery/data/500/422FEmotormountpad_65up-thumb.bmp

The change was made with the introduction of the FT Series (330/361/391). My guess is it had something to do with the more secure mounting of the truck engines even though most used front and rear mounts in heavy chassis applications.