From the web site of
www.4speedconversions.com The "621" Chevy Bellhousing is a 168 tooth aluminum bell with 4-5/8" center hole.
It was used on most Chevrolet Big Blocks,Small Blocks and Six cylinder engines requiring an 11" factory (Heavy Duty) clutch.
Considering the wide range of original usage, and the fact that it was in the General Motors parts catalogs until at least til July of 1987, you would think these units would be plentiful. Yet, this Clutch housing is so highly sought after, that there is now a reproduction available.
