I converted my '87, and it worked fine.
I used the Mickey Mouse setup from Advance / Zone, did a double flush just to make sure, and it worked perfect.
When you check to see if anything is now left in the system, don't hold the valve open too long until it all vents.
Hold the 'save the planet' rants please... All the people on the planet will fit within the confines of Texas. What do you think they could do to Texas/the South/the US/North America/across the oceans and the rest of the planet, if they all did it 24/7, from within the Tex borders? How much less could they do if spread out??? Don't know about you, but heating my home this past winter was NOT cheap. Gore and my local weatherman are failin' to communicate.