he ARG file are generated by the RBF2ARG tool.
Please find it attached the encrypted ZIP file (your last name as a password).
IIRC, the usage is :
for the MCC216 S-Video
rbf2arg 0 A <version.revison> "description" <filename.rbf> <filename.arg>
for the MCC216 VGA
rbf2arg 1 A <version.revison> "description" <filename.rbf> <filename.arg>
Then, you have to put the ARG file under /System/core and voila, you are ready to flash it on your HW.

As for the S-Video, I have attached the S-Video core.
It uses Direct Digital Synthesis (DDS). It needs clocks at 28 and 114 MHz but it can be adapted for 57 MHz.
It is compatible with PAL and NTSC providing you set correctly the "pal_ntsc" signal and the clock is 28.375 MHz for PAL and 28.636363 for NTSC.
BTW, I do not know how you generate the clock for your core but, what we do is : 
5 x 227 / 40 = 28.375
5 x 63 / 11 = 28.6363