How about a smash-up of the two? Bore out the mani, make a spacer to fit the weber between the stock bolts, mount the weber to the spacer, mount the spacer on the mani. Looks like there is enough room for the weber to fit between the studs on the manifold. Might be the best solution, you certainly wouldn't have to bore out the weber and chance messing it up. Also, less chance for vaccum leaks. Plus, TIG welding can get expensive, unless you can do it yourself.
Interesting idea. I would like to keep my stock manifold untouched if I go with the spacer. I do have the 78 spare though. I have the correct tools, so damaging the carb when relocating mounting holes wont be an issue. As for paying for welding, just look at the shop behind the manifold. Ill be doing the work
thanks for the input.