Why don't you re-run your calculation with the only change being D/R/I = 38/38/24?
Intercept,
That is actually quite easy. For each point you take off the Democrats and give to the Republicans in turnout, you would just have to add 1 point to the Gov and reduce 1 for the President
So, if we use the 87% Republicans for the Gov but with a D=R turnout, then the numbers would be R:50 O:47
However, if you use the 95% number for Republicans voting for the Gov, then the final would be R:54 O:45
Cheers!