They used a wheel hub that had a deeper offset flange, BMI karts has them as they bought out Dave Libberton's old HPE/muskin stock he had. I don't think you can find the one piece drum sprocket that HPE used, but the Lomart used brakes and sprockets also found at BMI, again out of Dave's old stock (he bought out parts lots many moons ago), can probably be made to work but you will have to drill some new mounting holes, and you can bolt on the sprocket to them. they used the same brake plate that the later cats used.
heres the link to BMI's vintage stock where those parts can be found:
https://www.bmikarts.com/Vintage-Minibike-Parts
you can see the brake stay tab pretty good on this duster chopper I used to own:
Heres the OG sprocket on the wheel:
and the brake plate: