You'll be better off to fabricate a new crossmember. It's a pretty simple job, using square steel tubing and flat plate. You're not likely to find a bolt-in item that will clear the automatic transmission bellhousing. Yes, the crossmember is important- - - -it reinforces the rear mounts for the front springs. The one shown in your photo is for a 1954 or later pickup. Earlier ones had a flat mounting surface for the bellhousing motor mounts for a 6 cylinder engine. It would need to be extensively altered for clearance of the torque converter area of most automatics.
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!