Hi,
I've installed both Lazarus 1.8 32Bit and 64Bit.
Then I changed the Compiler executable in Lazarus options to C:\lazarus\fpc\3.0.4\bin\i386-win32\fpc.exe
and in the Project options I changed the Target OS to Win32 and Target CPU family to i386.
This worked for me. I created 2 build mode 1 fr 32Bit and another for 64Bit. Now all I need is to change the build mode and Compiler executable each time.