Reply to "Weber Carbs"

I Don't mean to sound negative but if you are bored with your life, convert to Webers; that will give you (or a hired tuner) something to do for the forseeable future. In case you've never played with Webers before, your very FIRST purchase should be a good Halon fire extinguisher, as small backfires are the order of the day, and they can/will catch the air cleaners & anything close by on fire.
Your second purchase should be a Weber manual (3 or 4 manuals will be better), because there are 5 jets and two air-bleeds for each cylinder and they all interact to a degree while you are tuning. The venturis and aux-venturis also are changeable and there are no cold-start chokes; Webers use a fuel-richening circuit instead. The cheapest jet sold is about $5 so expect to accumulate quite a collection of part$ you will never use again and which are useless to most other sufferers. In engine fires, the aux-venturis are pot-metal and will melt.
Having spent a solid year getting a set of Webers running well with decent fuel mileage, if I was to contemplate abusing myself again this way, I would use a side-draft intake with Weber-lookalike EFI throttle bodies from TWM. D Quella sells a well-sorted EFI system that can use such throttle bodies or short style downdraft types both of which DO fit under a stock engine screen without cutting the decklid, and once tuned, do not change with every passing cloud in the sky. For $5000.
Did I mention there are Weber-copies available from China via E-Bay and late-night swap meets? They are excellent visual copies except for porosity in the castings plus all the usual far-east-copy probems. Some actually work, too.
Original Italian Weber carburetors were discontinued in the late '80s but one small division in Spain still occasionally makes "original" Weber carbs in a few sizes.
Finally, the 48 IDA and 48DCOEs are really too small for a performance 351C. What's needed IMHO is about 58 IDAs, of which there were exactly 6 sets ever made. But dune buggy off-roaders and sand-drag race shops have such carbs (& larger) available sort-of-reasonably. Not one single part comes from Weber, though. BTW, Jim Inglese sold his CA carb & injection business in 2010 and now runs a new one on the East Coast. The original 'Inglese Inc' is not associated in any way with him but both places sell more-or-less the same things. Good luck.