Which analog input and output units are you using? How precise (how many bits) are the inputs and outputs? Let's say you have a 16-bit input and output. That means there are 65536 total possible inputs, and the same number of outputs. There's a direct mapping of inputs to outputs. So, your lookup table needs to contain 65536 *2 elements, each of which is 2 bytes (16 bits), for a total of 262144 bytes or 256kb. The FPGA in the 9074 has 720kb of RAM, so more than enough space to store this lookup table. If either the input or output is lower precision, for example 12 bits, then it requires even less space.
You wrote "I failed to use LUT" - in what way did you fail? Have you looked at the help for the Look-Up Table 1D Express VI? How about this white paper?
By "cast the fixed-point value to an integer representation" I meant that if you are using fixed-point (not floating-point) on the FPGA, there is a fixed-point to integer cast function which simply tells LabVIEW to treat the same sequence of bits as an integer instead of fixed point. You may be able to set the analog input and output to use fixed-point (or raw integers) instead of floating point, which will be more efficient on the FPGA. If your only choice for the input and output is single-precision, use the numeric conversion functions to convert to fixed-point. The effect of making this cast is a bit like multiplying by 10 in that it shifts the decimal place to the right, but it's a free operation (requires no FPGA logic) unlike a multiply. To understand this further, read about fixed-point math.