I bought a '94 FW and will need to flush and fill the cooling system. Any problems with switching to Dexcool coolant that became standard with '96 models?

wont do you any good... and if you do you need to get every last drop and residu of the green stuff out of the dex-cool ill break down and not work right.

just use the green and put the addative in.

Ditto what he said.

There would be little benefit to using the Dex-Cool if it was not the "factory fill".
And merely flushing and getting "every drop out" doesn't matter either. The actual main benefit to using the Dex-Cool is found through the initial break-in period which is when the Dex-Cool coats the aluminum engine parts with an extra protective coating. It can only happen on a new engine and anytime thereafter, even the tiniest amount of "regular" green coolant contaminates the cooling system for good. Therefore you might as well just stick to a good quality standard coolant.