what adjustments would the carb need for a swap like this?

the lg4 was stock except carb/intake, and I'm putting hedman shorties on the 350......the engine was used, so I'm guessing around 300hp at the flywheel at most

Jets. Perhaps power valve, accelerator pump cam, secondary diaphragm spring.

eek. any recommendations as to what specifically I should get (jet sizes, etc)?

For jets, get the kit that has pairs from 66-99. You won't need them all, but what you will need will be in there, and buying individual pairs will probably end up costing you more by the time you get it tuned than this kit will. Plus, the kit has a nice box to keep them all in.

You might also want to consider a 4160-4150 conversion. That will allow you to rejet the secondaries more easily.

The Quick Fuel Adjustable Secondary Housing is a nice piece that keeps you from having to change springs in order to tune out bog. I prefer its operating principle to the spring stiffness change as well.

You probably have a 6.5 power valve now. The Holley web site has a good description of how to determine the correct power valve. Follow that (ignore the idle-vacuum method, doesn't work on mild engines), and get a different PV if needed.

Pump cams, shooters, larger pump diaphragms are also things that can be changed/tuned. You probably won't need to do those things, though.

I would just put it on and see how it works.

I guess I assumed that was assumed.

Sorry for being presumptious.

If the 600 has not been messed with ( has the factory jetting)
it should work just fine on the 350.

You can fine tune it with jets and tuning the accelerator pump
shooters etc but try it as is first.

Generally #64 to 66 primary jets , a 6.5 power valve, #25 to #28 accelerator shooter, # 9,or #39 or #21 secondary metering plate
works very well. #9 and #39 are stock. #21 is found on 750 3310's

The 600 usually can use a little lighter tension secondary vacuum spring than stock. get a purple or plain steel colored spring. Black (stiff) is stock.