I installed the single speed version of this fan, wished the multi-speed was availble when I did it.
I too had the Ventline OEM from the factory, the one with the very small and basically uslesw fan. I had to reposition the vent handle per the Vortex instructions, no issues with that. I used the existing factory wiring to power the Vortex.
There was a metal junction box inside the the OEM vent that interfered with the Vortex fan's fit, I simply cut out the junction box, used wire nuts and wrapped the connections in elec tape, proceeded with the installation.
I have had no issues in the 18 mths I have had it installed.
2007 Chevy Duramax LMM/Allison
2012 Jay Flight 29QBH
2012 Jay Flight 26BH (Sold)