I used Lobaugh 42" wheels on my Lionel FEF. I no longer remember whether I had to drill the journal boxes or not. If I did drill, it would have been after careful measurement under a magnifier, a careful center punch, and a final drilling with a #41 drill and cutting fluid. I doubt anyone ever made 41" wheelsets.
Before I became so careful, I drilled a Lobaugh Centipede set of castings. Just a little error, and I wound up cutting it for sprung bearings to make it track. Measure 3 times, drill once.