RVs powered by a Ford V12 are exceedingly rare; if they exist at all. Ford's last production V12 was phased out in 1948. It was used primarily in the Lincoln Zephyr model from 1936-48. Sorry, but I couldn't resist.?
Are you asking about the current Ford V10 units, perhaps? That's a pretty common engine used in gas-powered Class A motorhomes and has received good reviews for the most part. The primary complaint has been that it is a bit noisy in high-torque/high-RPM situations, but much of that is related to the fact that the engine is front-mounted in the Ford F-53 chassis so it is in close proximity to the driver position.
Ford has recently come out with a big-bore V8 that is designed for motorhome use in the F-53 chassis. I think the jury is still out on whether the new V8 will outperform the V10, and/or replace it entirely in the future.