[kurlannaiskos]

personally , I think it is a lot easier to swap cowling parts (especially around the exhaust) than to swap entire noses.
the Soviets did modify G's to have navigator/bombardier stations ,but these modifications were done minimally.
the access panels to the guns and ammunition were removed and replaced with perspex.
this is a lot quicker and easier than swapping out the entire nose.
I have also seen exhaust styles from A-20B's and A-20C's on A-20G's ,so don't be fooled by that.