The modifications to the mag catch can be done in less than one half hour using Swiss needle files; even quicker if a Dremel Moto-Tool is used. I'd suggest modifying a GI surplus mag catch so as to avoid damaging your original West Hurley catch. Take care to maintain the original profile of the locking king stud and the angles on the notch groove. Complete the modification by touching up the bare metal with a cold blueing solution and you're done.
Right side view of mag catch (out of housing)
Original, Colt, WW II, and unmodified W/H mag catch. Note that the front lip of the locking stud is level with the rear support arm. Proposed modified mag catch for W/H semi-auto (only) guns to allow the use of unmodified, original full-auto magazines. Height difference is exactly 0.1" from original dimensions.

The only reason I brought up the mag catch modifications was the recent acquisition of an other-wise pristine "20/24" 20 round mag that had been butchered into a semi-auto mag (reducing its value from $45 down to a $3 paper weigh) Maybe sharing this trick will help us from losing any more collector magazines to shooters. After all, replacement mag catch costs $15 which is a lot less than the loss in value to one collector magazine.