Sure, fully 16-bit Windows 3 is
less picky than mostly 16-bit Win 9x. No 512MB RAM silliness, 350MHz limit (AMDK6UPD.EXE patch) or 2.1GHz limit. Someone did it
here.
For best compatibility though I'd suggest using the last chipset to fully support 9x (i865 or i875, yes you could get AGP with Core 2) although you don't necessarily need to install any chipset drivers. And the most compatible AGP card is likely a Voodoo 3 (because it supports no AGP features at all and simply treats AGP as a PCI-66 port).