put a l style corn head on an r50 when they said it can't be done? the l throat is about 60" wide,allows you to center on machine,have to add or subtract auger flighting to move cobs to feeder house, fill in the unused L feeder area, drives can be made to work like your grain head attachments ETC>ETC. still a pile of work but back then they wanted $25.000 for new R style head and I could buy an L3 6 row for $8,000 that only did 800 acres good luck!
done several, used to use Bish adaptor. Now just take combine and pull it up to throat of header, line up everything, and fabricate top lid or frame, reverse the drive shafts left to right, slot the holes so shafts can be moved reaward an additional inch and cut holes for roll out hooks to latch on with a reinforcement plate for botom latch. Bish offsetts the head as it is centered on the throuat head , we mounted them heads up on the rows with the throat offset as the hugger heads are. In this case the shafts have to be set up a little different - can't remember the exact details.