I believe the purpose of that adapter is twofold- - -it converts the Chevy bellhousing bolt pattern to the SAE pattern for medium and heavy duty transmissions, and also allows the use of a larger diameter flywheel and clutch assembly. If you're doing real truck stuff it's definitely an improvement.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!