you didnt search very long.
there is no "best" combo. you can probably pretty safely say all of the _better_ combos are going to be with AV10 setups. av10 was the euro model... its case inducted with reed valves as opposed to straight up piston port like your av7, so even stock its better right off the bat. Plus the fact that the frenchies overseas made all sorts of aftermarket parts for their AV10s (kits, variators, pipes, springs, hardware, etc etc) leaving american AV7 technology in the dust.
like paul says, though, you can get an av7 to do 45 all stock parts if you know what youre doing. maybe even faster. look into porting, a pipe, a varplus, milling your head, changing your gearing, for the best AV7 setup.
i may be oversimplifying but in terms of kits, there's only about a handful for AV7... plenty of 50cc cylinders around... either stock repros or improved upon stock design, the 74cc airsal you're talking about, 62cc malossi (RIP) and the 70cc parmakit at treats. either of those big boy kits are going to necessitate a tuneable carburetor... dellorto SHA wont cut it. Dellorto PHGB seems to be the fan favorite in motobecane. for av7 pipes the G3 seems to be the most favored due to its low (relative to other pipes) and wide powerband. a decent rule of thumb is any moby pipe under $100 is garbage (pires chrome, leovince cobra).
once you get into AV10 its a whole different ballgame. you'll need deep pockets and know how but av10 is where its at for the best performance. treatland.tv has everything you'd need, and you'll need quite a bit building most of a new engine from scratch. cases, reeds, intake, cylinder, maybe a new crank, maybe a new head. There are plenty of cases and kits and pipes to choose from, but once you get into the big guns youre going to need all of your peripheral equipment up to snuff as well.. variator, pulley, maybe a clutch pulley, return springs, belts, bla bla bla.