I found the same answer, but I got a email from m.m. today with 4 pages of instructions on using a "501" kit and converting you 203 using a wedge kit. I tried to download the files but they are too big. If you want I can forward to your email, but need your email address. Sorry I am not too good with computers. I am going to look over the 4 pages tonight and see what it entails.
You could also call m.m. and ask them to send you the "wedge" kit instructions, either way I hope this information helps you. Tom