Rupp Drive Chain or Torque converter ???

Mini Bike & Go-Kart Parts

Hello everyone. I need some help from a pro...
My old Rupp Scrambler from my childhood I decided to restore and give to my son. I lost the original motor and just had a rolling frame. I bought a 79cc Predator motor and was planning on putting a torque converter but heres my pickle. both of these spindles are 5/8" and all the torque converters are 1" or 3/4" to 5/8" drive??? What would you use to get this bike rolling. I could buy a clutch and sprocket but dont know teeth numbers or size. I would appreciate any answers that are specific... Rob go buy this and she will work :) or if you have something to sell me even better.

Thanks in advance and Merry Christmas
Im pretty sure you can buy an adapter sleeve to go from 5/8 to 3/4. then you would need to fit the driven pulley on the jackshaft might need a new one all together if that one isnt long enough. I think the torque converter would be the better route in this case for a kid because they are better at going slow without burning up so your gearing wont be as important.