OK, just the basics . . .
The ECM relies primarily on throttle position, manifold vacuum, and the feedback from the O2 sensor to control the A/F mixture in the CCC and the distributor spark advance in what is called "closed loop" mode. If your engine has a knock sensor it will take that into account too. Some do some don't. Anything you do to alter these inputs to the ECM effects its output control behavior.
Just moving to a 350 staying 9:1 or less on CR will not effect any of these significantly enough for the ECM not to handle it. The additional displacement may require some alterations to the idle circuit of the CCC to get it to idle properly. If you have access to the idle mixture screws you may well be able to just enrich the idle mixture slightly to suffice for the additional displacement. Two access holes should be visible right at the base of the carbureter in front. If you do not, procedures are available on where to drill [carefully] to gain access to them. Or, you can buy a rebuilt unit that already has them exposed [almost all the rebuilt ones do if yours does not and you do not feel comfortable doing the drilling yourself]. Worst case, if screwing the mixture screws a few turns still does not make it idle well and you are finding you have to keep screwing in the idle speed screw until the primaries are slightly cracked open to get it to idle, then you have to make some minor modifications to the idle bleeds to allow for more fuel at idle, perhaps adding a small hole in each primary butterfly to add the additional air. I had to do this to get my big block to idle off the CCC. I really don't think that will be necessary just going to a 350. You then will likely need smaller secondary metering rods for open loop foot to the floor performance to feed the extra displacement. The ECM is completely out of the picture then though.
Where you run into problems is adding enough cam duration to start effecting the idle/off idle/light throttle manifold vacuum curve enough to confuse the ECM which makes it start to misbehave. I would personally not go over about 260 max duration, stick with 112 lobe separation, and not more than .450 lift if you expect it to run reasonably well with the factory ECM. But, a 9:1 350 with that cam, CCC, Performer intake, good crate heads or mild headwork on stock heads, wouldn't necessarily need headers but wouldn't hurt, into true dual exhaust, will wake up that Elky quite nicely.
There is one other area where you can run into trouble and that is during, OD, lockup, when the ECM will be closed loop and place the engine in what is called "lean burn" mode to maximize fuel efficiency. You will see A/F ratios exceeding 17/1 [14.7/1 is nominal at sea level] and then the ECM dramatically advances the spark so the the engine runs without pinging. We ended up with max spark advance during lean burn of like 63 degrees to get my big block to not only purr in lean burn without knocking but had to move from like 17.7/1 which was the stock max on my 9 engine back to right at 17/1 max was as lean as we could go. But, that yields 18-20mpg with my big block. My 67 gets 14. Some aftermarket chips just punt lean burn altogether but there goes your mpgs. And some aftermarket chips absolutely do nothing. Sorry, I don't have a list of good/bad chips on that account because we did a custom chip. Hopefully others can chime in there.
Sadly, the guy I worked with up in Toronto on mine 12 years ago has moved and I've lost touch with him. I would send him laptop dumps, he would rebuild the tables, and send me a new chip. It only took 3 tries to get mine right.
But, I'm not sure you will need that . . . if you keep the 350 fairly tame.
I'm sure I've left something out but this is a good start . . . I hope?