420ma op amps
As a general outline, use a 324, you may find it easier with more than one op amp.
Convert the 4 to 20 mA into 2 to 10V by connecting across a 500Ω resistor (or 1 to 5V across a 250Ω), buffer and subtract 2V (or 1V), apply to gain of 1/8 (or 1/4) and buffer the output. A lot of this can be done around only one of the op amps but I like to buffer outputs if I don't know what its driving. Also be aware that you may not be able to drive down to 0V.