225 head pipe

Can't seem to find a 2.25" or 2.5" (or super six) head pipe for my D150 slant six. Anyone know of somebody who sells these?
I have a couple of TTI 2.5" head pipes. They're not the full length, but they stop about right under the driver's floor. Plenty to hook an exhaust to. I'd suspect for a truck, you'd need to cut the flange off and add some for more height. But I don't know.