As you are probably aware the major vendors don't count the logic resources in a fpga in any logicaly consistant or meaningfull way however the t51 core with the hardware multiplier/divider unit included but with no timer/counter units takes about 2200 altera logic cells plus 4kbytes of dual port ram.The smallest device i have fitted it into was an altera EP1K50TC144-1 where it will run at about 35 Mhz however it does benefit from moving to an altera cyclone or xilinx spartan3 where it can use the built in hardware multiplier and fast carry alu logic and will then run at about 85 Mhz.