Looking at the brew day sheets Denny has, I'd say the BYO recipe isn't too far off, but they undershot the adjunct. It looks like they totally missed the syrup (a high dextrine brewers corn syrup, it looks like) used in addition to the grits, bringing the total fermentables from adjunct up to about 35% in my estimation. If you adjust the flakes in that recipe to around 30% (assuming you get more yield from flakes than malt on your system) you'd probably be getting close. (I also see no point in including 6 row. Back then 2 row and 6 row were different. Today's 2 row is indistinguishable from 6 row, which is why 6 row is vanishing.)
I've been really going down the rabbit hole trying to work up an adaptation from those records, delving into Milwaukee water reports, trying to identify the acid theywere using to estimate mash pH, and such. I want to brew it but may have to wait for the new hop crop to find any Cluster and Fuggles. When I do, if Denny doesn't think it's publicly revealing any privileged information (any more than BYO did,) I'll post my version. But I think what I said about adjusting the BYO is a pretty good start.