Rear crossmember exchange

I need to cut out and change my rear crossmember,what’s the best way to do it???

Sawzall with a long blade, you can do most of the sides and the botton of the chassis with the 4.5 inch grinder with slitting discs, but defo need the sawzall for the top face.
OS chassis has the wiring loom in it, tie a stiff piece fo wire to it and pull it from the front of the chassis until its out of danger.
90 and 1110 have the same chassis loom so 90 has loads of spare wire tucked inside.