I am not sure you can target the x86 platform and have it run within an x64 instance as it will be executing in an x64 thread. You could target Any CPU or x64 but if you do that your VFP driver will need to be built for the 64-bit architecture which you said does not exist.

An option for you, run 32-bit SQL Server on 64-bit OS. It will relieve some of your memory issues (4GB user mode VAS instead of just 2GB (or 3GB with boot.ini switch)) and with AWE you can address more than 4GB for your buffer pool.