Blown, you are obviously in love and thus not entirely rational, so a couple of more facts. If you or someone reading this post finds one of these blowers for sale in which a screw or other metal object has gone through the rotors and scarred them or the cases, and you can get it cheap, do not throw it away or waste time trying to find a shop to weld and remachine the cases (which will hopelessly distort even from TIG-weld heat). Scarring is common with roots blowers both the aluminum and magnesium case ones. I have a close friend who builds blowers for big-name dragster guys. I asked how he fixes scarred cases, and he said, 'JB-Weld'!
Clean the scarred area with solvent, deburr if necessary and wipe on JB-Weld epoxy with a plastic bondo-scraper so the result is level and has no high spots. The cases & rotors never touch so there's no load on the repair. My friend says JB-Weld is fuel-proof once cured for a day or so, and if you're careful in applying the epoxy, the repair need not even be sanded.
Keep in mind most 351-Cs have thin cylinder walls so you cannot safely increase cylinder pressures much. Sonic-test any donor blocks before considering supercharging; I personally blew a silver-dollar-sized piece of cylinder wall into the water jacket on an 11:1 c.r 351-C when it 'sneezed' on the start line of an event- probably due to not being fully warmed up. It had a fairly big flat tappet cam, a big Holley carb and aluminum heads but no nitrous or supercharging. This was on race gas, too. We later found the block had been bored 0.030" over and at the point of failure near the top of the bore, the failed cylinder wall was only 0.075" thick. We were lucky the rings originally seated- walls that thin flex a lot! Pro engine builders get nervous when cylinder walls get below 0.125" in a performance build and that excludes many (most?) 351-Cs. It's worthwhile to look for a good one.