Hi George,
Just shooting from the hip and, you asked! I suspect that apart from the new-build of DB605AM and ASM for new production 109's, the large scale remanufacture of 109's would have included upgrading aircraft to the MW50 standard on rebuild/repair in some sort of program after about Jun '44. I would also suggest that because the fitment of the large fuselage tank was only possible on newbuild /rebuild, the initial rate of conversion of GM1 to MW50 equipped aircraft would only be relatively slow as, I do not think there were that many GM1 aircraft to convert?
Over to the production experten!
SM