I used to run a TQ and a Holley Spread Bore on my 340. Swapped them as I felt. I also used square bores as I wanted too.

For me the TQ was temperamental but when it ran it ran better then a Holley. The Holley was consistent.

I never noticed a difference in the performance for the spread bore vs square bore when I swapped them out. It always seemed to be a matter of tuning and design.

I would say for me the Carter's gave more power but since they were metered with pistons and springs they tended to "hang" and be more temperamental.

If you like that spread bore sound but holley tuning simplicity. Run a Holley Spread bore. I was just at a swap meet and there must have be 10 of them for sale for $50 each or less.