Let me make an alternative suggestion- - - - -how about installing a wheel-lift boom, but lifting it with the conventional cable winch? Find a period-correct wrecker bed for the chassis, and install a modern wheel lift under the rear. Since you're not planning on doing a high volume of towing, or any recovery work, it's possible to hand-adjust the boom, or even use an electric-hydraulic setup for extending the wheel lift in preparation for towing, then use the cable winch to do the lifting. Just hook the winch cable to the wheel lift instead of using the old style sling and A-frame cradle.
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!