You have a few options.
1) the Thermoquad can be rebuilt. There are kits around to that, but it’s a complex carb. There are people who can make these carbs work.
2) find another Thermoquad better suited to your engine, will probably still need rebuilt.
3) find a new spread bore replacement carb.
4) find a new square bore carb. Best to change to a square bore intake, but there are adapters to do this.
Properly set up, the Thermoquad is a great carb.
1) the Thermoquad can be rebuilt. There are kits around to that, but it’s a complex carb. There are people who can make these carbs work.
2) find another Thermoquad better suited to your engine, will probably still need rebuilt.
3) find a new spread bore replacement carb.
4) find a new square bore carb. Best to change to a square bore intake, but there are adapters to do this.
Properly set up, the Thermoquad is a great carb.