I always weld them up. It’s worth 12-15 HP and it’s a ton of work to do it correctly. The gains come from getting the distribution closer between the cylinders.
Someone...it may have been
@12many or maybe it was @MoparSam who modified the top without welding. It turned out very nice.
If you are wanting to pick the fly poop out of the pepper then weld it up. If not...send it.