All the 1911 conversions I know of have a feed ramp built into the .22 barrel that completely bypasses the pistol's built-in feed ramp. M1911. ORG recently tested a conversion and tried it on both conventional 1911s with frame feed ramps and on a para-Ordnance pistol with a ramped barrel, and it worked on both.
Here's the review. Scroll to the end for the discussion of fitting the conversion on the Para pistol: http://ezine.m1911.org/showthread.php?t=142