The Superdart came with an Airheart disc setup.
The bracket on the frame is for the master cylinder.
The caliper is an Airheart 150 series.
To mount it you'll need the bracket that uses the bolts
where the rear axle bearings are.
You can get that from Greg Gouvella @ "Greg's Speed Shop".
He has a website.
If he's out, you may have to wait until he does another run of them.
It's raining pretty good now, when it lets up I'll go to the shed and get you some pics.
If the disc setup is too pricey (new, the m.cyl.,caliper,disc,hub,
lines,fittings, and fluid will run about $300-$350) you can go with a Bendix drum brake on the rear.
Comet Karts has those but be advised the word is the drums aren't up to the standard the old ones were and can bellmouth under heavy use.
There are billet finned drums available but they aren't cheap, either.
If you're not going to be racing your kart the stock drum should be ok.
You can also use a modern MCP disc set up for fewer bucks if you want to stay with the disc.
---------- Post added at 10:30 AM ---------- Previous post was at 10:08 AM ----------
Here's the bracket.The dimples are so you can drill the third hole to align with the bolt holes on the bearing cassette.