I haven't, but that might work. Are you sure the 4100 has "frame extensions" for bumper mounting and is not just a longer and differently shaped frame at the bumper?
The 4100 frame is nearly identical to the 3800 except for bumper mounting. The larger bumper also uses two bolt on heavy channel brackets to further support the bumper corners.
The splash pan between grill and bumper I believe is different as well. If different check how the big truck splash pan looks with little truck fenders?

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-