Harbor freight air over hydraulic pump. Cheap. Then just get a Hydraulic cylinder or cylinders off of something that has the same length. Porta power or jack. There are plenty of sources out there. they are cheap new do a search. I wouldn't put air back on your asking for failure again. Hydraulic will push more weight. We put one of those pumps on this 10 ton frame puller. It works better than the one it came with.
10,000 PSI Pneumatic Hydraulic Pressure Pump
https://www.walmart.com/ip/Hiltex-1...47731041&wl0=&wl1=g&wl2=c&wl3=98124798290&wl4
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