Given the relative scarcity of board with FC-PGA2, AGP and ISA, I'd start off with "any you can find". I'd agree with the VH6T as one of the best options, but unlikely you'll find one...
Alternative is of course to go for a Slot 1 board with Tualatin BIOS support. Most Slot 1 is i440BX, which is fine but you'd be overclocking chipset, AGP and PCI for 133MHz FSB, which you may not want. Alternative is a Via 693A or 694X chipset that natively supports 133MHz, they can also be found in slot 1. There are other chipsets which support 133MHz FSB (and Tualatin), but are rarer and almost never seen with ISA. I'm hunting a SiS 635T board at the moment - this might well be best performing So370 chipset, but none of the handful of boards with it have ISA. Also, most are uATX (which I like, but you don't).