Bobcat 463 and S70 are totally different. The next newest model to the M371 was the 310. I do not believe it is the same ROPS though.
If you are needing a ROPS, they are not overly complicated. With a little bit of roll bar tubing, cattle panel fencing ,tubing bender , sheet 1/8" steel for the roof and a welder, one could be fabricated. Modern roll bar tubing is more than enough to support the weight of the M371. Cattle panel is just to keep the flying stuff from hitting the operator. You could double it up if you needed to make the openings smaller.