Strange way to brace a frame. Massive tubes welded in for no apparent reason, but no bracing around the highly stressed areas like steering head and swing arm pivot. Seems to have been done by someone with no clue about stresses in a motorcycle frame. No personal offence intended if it was done by someone on this forum. I'm just saying what I think. And what I think is that it doesn't make sense.
Hey Jim, I'd cut those additional tubes out if it was my frame. Like Chris already said, they'll be a pain in the arse for carby installation unless you wanna run with a manifold and a single carb. I reckon the 1-3 manifold should have a vertical intake stack poking up between the tank and seat, then you can plonk a vintage Zenith downdraught car carburettor on it with big old oil-bath air cleaner
While you're prepping the frame, it would be a good idea to put some bracing around the steering head where the old triple frames are prone to failures. There's plenty of info on the forum about cracks around the steering head and various bracing methods to prevent it.
Cheers,
Cam