/////Will the 82' or earlier fan and shroud will fit an 84 Blake 
Model Avanti to (facilitate) switching from the electric set fan set up. ///

The shroud will work.  I just put one on my 85 (Blake 305HO). The 
shroud looks identical to the one in my 83 (Altman, chrome bumper 
plain 305 -not HO).   KenMatson@aol.com