Moral of this story: ask the vendor which swingarms their bushings will fit. If they say something like "all CB750" then find another vendor: they are NOT all the same size in the 750.
I think it depends on which make / type of replacement bronze bushing is being used Mark. We fit the same bush to all model Honda CB SOHC 4's 1969-1978. We've never had any issues on either our own bikes, our restoration bikes or customers bikes and a lot of members of the UK forum also use bushes supplied by me.
I've only ever used or supplied the one type of bushing and over the past 9 years have sold / used about 500 pairs with no issues.
Bryan made a good point earlier, it's usually the pivot bar that wears if anything, especially on the higher mileage bikes, so it's always worth looking at that as part of a refurb.
I have seen (here) some bronze bushings, back in the 1980s era, which were good ones: they were in my own 750 for almost 100,000 miles before they wore. But, starting in the 1990s (probably with the advent of CNC machines everywhere) every mother's son started making bushings for these bikes (because Honda's own have been junk since their 1980s MIMs type came out). The problem was always the same 2 things, either:
1.) lack of proper tolerancing on those that they made with flanges on them to mimic Honda's 1976-and-later phenolic ones, so the swingarms simply jammed tight when the bolt was torqued. The flanges had to be 2mm +0/-0.1mm thickness, and if made that thin they cracked off as soon as the pivot bolt was tightened, and then ground up everything with its pieces in short order.
or:
2.) the makers assumed Honda used 1 swingarm bushing for all the bikes. As explained earlier, this was never true. The 750 had 3 distinct sizes (early straight bushing, later straight bushing, and flanged bushing with the later straight one's dimensioning inside the pivot). The CB500/CB550 before 1975 used the 750 parts, and after that used the later straight 750 bushings and collar.
The collars changed, too, as many folks know: the early ones had grease passages inside the bolt that were fed from the outer ends that put the grease directly into the pivots, while the later ones were solid and the grease zerk was moved to the center of the swingarm pivot. But this version required greasing on-schedule or else the OEM grease hardened in 3 years' time and no further greasing was possible. These are the arms I see the most, with old grease so hard in them that it can't be crushed without pliers.
The 2 different collars also made a big difference in lifetime. The early ones were slightly smaller OD and had the grease grooves and inner passages, while the latter are an actual interference fit (0.00" or 0.00mm) between the outer half of its bearing surface and the bushing itself, so until the pivot gets so hot from friction (and engine heat) that it melts the grease (if any) from the central grease zerk (which is spread across 1/2 of the length of the collar) it then becomes oil and works a little bit of it into the outer half of the bearing area. Obviously, if the swingarm isn't greased every 3000 miles/4500 km even this paltry lube won't happen.
I suppose that living where I do (Rocky Mountain region) makes this a bigger issue, as good handling is as important as solid brakes and truly good tires are when riding here. Bikes that don't handle well either hurt or kill their riders here, or get sold to someone else. So, I do quite some suspension work more than when I lived in the flatlands of the Midwest.
