Unimog Club UK

NO never drill or weld a Unimog chassis, there are several chassis mounts to work off.
You really need a crane base because your chassis flexes from corner to corner if you bolt to this you risk stiffening and that can cause the chassis to tear.
My 406 Doka has a crane mounted on the back this made sense because it's wasted space I used the implement mounts on the back but you must use a pivet point on the front where the linkage Rams mount and that will get in the way of the spider frame ( where your body mounts to.
A very small crane could be fitted to the implement mounts but not a 2.8 t per meter it's the leverage on the bolts that's the issue. proper crane bases are expensive 2k plus second hand.
Moose