immortal1 (linn)
+1y
Did this to my purple truck many years back - the heat gun method worked very well IMO. Once the metal frame for the radio was installed in the trim panel and the trim panel installed in the dash, I literally stuck the heat gun thru the metal frame and warmed up the plastic air duct. When it was hot enough, I slid the head unit in (with some tape over the back of the head unit so as not to get any extra plastic where it did not belong) and let the air duct form aroud the back of the head unit.
Hope this helps.