If you already have some DDR, keep it for the time being for testing. I would say your motherboard is going to be the hardest component to find.
My AI7, I feel gives up somewhere around 280-290 fsb w/ my 2.4c. I also have an IC7-G that I have booted the P4 2.4c into windows and stress tested for a while at 307 fsb. That was unstable however so I'm not quite sure if the motherboard is stable at 300mhz, as I know the P4 2.4C is not stable at those speeds.
Once you select a motherboard, there are a few differing thoughts on DDR. You don't need to worry so much about running in synch with the fsb as you do with the AMD XP cpus. There are usually 1:1, 5:4, 3:2 ratios to run in the bios.
Assume you find a motherboard that runs at 300mhz and the cpu is stable at 3.6ghz. You could run the DDR at:
1:1 ratio - DDR would be at 300mhz - very unlikely
5:4 ratio - DDR would be at 240mhz - some (OCZ gold?) PC3700 will run tight timings here, but most PC4000 is loose cas 3 timings. If you can find them, some BH5 DDR will do cas 2 if you slap it with alot of voltage. Also some newer samsung chipped Corsair Ballistix will run tight here similar to BH5, but pretty expensive.
3:2 ratio - DDR would be at 200mhz - any PC3200 will do, but you should look for cas 2 stuff here.
Overall, it seems that 1:1 memory at cas3 performs about the same as 5:4 memory at cas2, so it's not nearly as critical as an AMD system. Once you select a motherboard and test the limits of the cpu at a 3:2 ratio, select your ram based on which DDR speed falls in your performance budget.