Flywheel ID

That casting number was used on standard 63-66 289's with 3 or 4-speeds. It was also used on HiPos but the HiPo flywheel was balanced differently. Check the back side, a Hipo flywheel can usually be identified by an orange paint duab and a Brinell hardness test mark.

It must be the original ring gear if it has 160 teeth. In the late 60's the 160 tooth gear was replaced by a 157 tooth gear.

Here's some other threads about this:

http://www.hipomustang.com/hpmx/topic.asp?TOPIC_ID=5208

http://www.hipomustang.com/hpmx/topic.asp?TOPIC_ID=6513