Faster than rated for Ram

for amd non hammers, can you just by PC 3500 RAM put it into you motherboard, and just set it at whatever the mobos max ram speed is? (So it thinks its overclocking PC3200 alot but really its underclocking PC 3500 a little)

Whatever ram you have in the motherboard you can allways change the ram speed it's running at within the limits the manufacturer has set in the bios. The pc3500 ram might allow you to set a bit higher speeds with lower voltage before giving errors, though this is generally achieved by lowering the timings.

Amd processors usually prefere lower timings over higher ram speed, ofcourse it's best if you can achieve a balance between both.