I have a 4310, which is 32 hp. I think it is in your hp range.
I have a 655 tiller and can say it seems bullet proof. The skids for depth control need to be thinner to let the tiller go deeper. It seems to only tilll to a depth of about 6-8 inches.
I have a king kutter 72" box blade for grading drives. I need the MFWD when it is full. Does a great job. The KK is not the handiest design for changing the depth of ripper shanks but does work. I would heartily recomend a hydraulic top link for any BB work.