Mark,
There's also Pacific Crest Pipe Repair (
http://www.piperepair.com) - the feedback I've read has been overwhelmingly positive about them.
I recently used JB Weld to fill in a small dent in the headpipe plus five stamped-in recesses where heat-shield mounts had been on my MR175 pipe; it worked great. A few days ago the headpipe repair took a direct hit from a big branch while smoking hot, and all that happened was the paint scraped off the JB Weld.
If your dents are less than 1/2" deep, the JB Weld should be all you'll need. If you send off the pipe for repair, the JB Weld would also work well getting rid of any remaining dents or ripple from the straightening process. I've never been a "Bondo repair" kinda guy, but I would use this stuff again in a heartbeat.
My mashed-up OEM CR pipe is long gone, but the Retro Rocket and LOP pipes I have here both stay low, under the swingarm. I'm a fan of high pipes these days, and just finished installing a Jemco CR125M up pipe on my 175cc CR (lots of work, but worth it - just thought I'd mention it in case your '75 turns into a rider instead of a restoration). Jemco may make a CR125M low pipe too.
Ray