Weld on the outside of an installed nut....the heat will help loosen the stud, and the weld prevent the nut comming off the stud.
I loosen the engine mounts, one at the time, and place a jack under the motor to tilt it ever so slightly,...when installing headers (when studs are used).... install the RHS first, as tilting towards the PowerSteering w/headers in place might require you to loosen the PS.
Nuts requiring 1/2" wrench are easier to install than nuts requiring 9/16"....
Also there are a LOT of ****ty exhaust gaskets on the marked.
I get mine cut out of same gasket material used as used for truck turbos....and I re-tighten the nuts after the first day of driving...
I'm also a big fan of installing some type of flexible joint in the exhast pipe.....
2.5" pipes do not flex much,...but the elephant engine will tilt quite a bit.....and a rigid exhast system transfers forces onto the headers...