You are right the only backhoe that outreach the Mustang/Gehl 7810 is the new Deere 710 J, my friend has a Case 590 Super M, and I outreach his with my 2109, I can load trucks faster in tight quarters than any backhoe.
Mine has the Perkins and never have any problems at all, Good luck with your machines, report back if you have any problems.
I've got a extra engine laying around if / when you need it. I don't trash the machines because they're the best you can get but perkins messed up and the reps will tell you about it if you ask. I filed a lawsuit against perkins / gehl because of the perkins engines, won, and got them replaced with cummins. It was honestly not gehls fault (but my contracts were with gehl/mustang not perkins) and perkins went bankrupt shortly there after to absolve themselves of any further legal problems. Personally I like the cummins better because they have better low end torque than the perkins.