I am preparing to do the same thing.
I may keep my CMC windshield and modify it to fit the MG parts I have consisting of Cowl Brackets Moss PN 408-315 & 325 and Side Supports Moss PN 408-230 & 240.
I still have to purchase miscellaneous bits and pieces to make it work.
I am not sure if the convertible roof needs to be changes but if I keep the old frame and glass with the CMC attachment system I think it should be simpler than replacing the complete windshield.
Does that make sense and are there problems with my thinking?