+1 i had a custom rad quoted and it was right around 500, a couple years ago.
Check out AFCO racing radiators, I bought one for my RX-7 (it was made for a chevy nova) when I did a v-mount. It is double pass and I had to re-weld the inlet and outlets for it to work. It was like $189 and it works awesome. Its also ultra light. They make all sorts of sizes and styles, and with a hack saw and some aluminum tubing, you will probably get what you want. There are plenty of welders in the area that can weld it for you, including me, and you should be able to do it for well under $300.