Drifting a bit off topic but I vaguely remember a "/passive" switch but could be wrong. I tried it with ACE 16 and it doesn't appear to work. There may also be a registry setting you could temporarily rename to get the 64-bit provider to install with the 32-bit install already present.
For some reason, I can install the Office 10 32-bit provider on my system even though I have 64-bit Office 16 Access installed on my system.
You likely already have this figured out but this quick and dirty detects the bitness of the installed provider:
Text = "None"
if RegExistKey( @REGMACHINE, "SOFTWARE\Microsoft\Office\12.0\Access Connectivity Engine\Engines\ACE", 32) then Text = "32-bit" ;
if RegExistKey( @REGMACHINE, "SOFTWARE\Microsoft\Office\12.0\Access Connectivity Engine\Engines\ACE", 64) then Text:=" 64-bt"
Message("ACE Version 12 providers", Text)
exit
The script reports "32-bit" as expected.