I have been looking at this for awhile now and plan on putting juice brakes on my 77 GS 340. I know, "Whaaat?" But the thing is that the stock handle is too far away for the kids and even if they can grab it, the sled doesn't really stop. This has already cost me a hood and very nearly an irreplaceable perfect bumper!
I have been told, and am now looking for a handle and caliper from 95ish Polaris Indy. I can make a bracket from there to make that fit and have the larger GP 292 disc. If all goes well, my 70 SS 338 will get one too!
I agree with you guys on the race sled and as the stock cable brake stopped the track, could never see the big deal, until I bought my 98 SRX. One day while playing with the SRX and my old 750 back and forth, I forgot which sled I was on and very nearly ran the 750 into the trees! The SRX is unreal stopping power by comparison, for daily riding juice is the way to go! G.