What problems do you have with the stock suspension? I always thought those cars handled pretty good they way they were designed, a whole lot better than American cars of the same vintage.

Concerning the rear axle, you are wasting your time and money changing that out. You are talking about completely different designs. Plus, the swing axle is actually a pretty decent design. It doesn't handle too bad and is great in the snow. I would just replace the rubber bushings and center boot and call it good if there is nothing else wrong with it. They sure look funny if you have the trunk loaded down though.

I know the front suspension is a totally different design as well. The W115 is a lot closer to the W123 than it is to the W110/W111 (front and rear). The W114/W115 cars were a major redesign. I'm sure all the mouting points will be totally wrong. Again it's not a bad design if maintained properly (read greased every oil change), and nearly bulletproof. Also not sure why you want to change the rotors. The front disc brakes on the W110 are pretty good. I think they have a piston on both sides of the caliper as well. If it is cost of the rotor you are concerned about, they can be ground, or a new one will last longer than you. I'm pretty sure the later W110 cars did have a bigger brake booster that can probably be retrofitted fairly easily.