The clutch/belt driven PTO pumps can be fairly heavy duty and are used on a regular basis on tow trucks that use a lot of hydraulics simultaneously.... rate your pump by GPM and PSI - your engine provides the HP. Most pumps I am familiar with run 15 -25 GPM @ 2500-3000PSI which is more than enough for that little crane. The issue is that they engage using 12 volts not 24...
I got a deal from Boyce about 7 years ago on a transfer case PTO and ran my hydraulic pump that way. Make sure that who ever sells you the transfer case PTO also includes the Yoke (as well as the oiler tube) - it is a tapered shaft and would be a PITA to find an easy replacement. I just attached a shortened front drive shaft and a couple of specialty U-joints (the Transfer Case yoke and Chevy yokes are different sizes). I put the PTO cable nob between the front seats. So I put the T-case in neutral, pick a gear I want to run the pump in (usually 3rd), and while slowly releasing the clutch I pull up the PTO cable and feel the PTO engage...
If you are mounting it behind the cab, you will have fun like I did and have to shorten your bed and move your fuel tank... good luck!!!