I have a 2.4 in my GT and I can answer a few questions. I didn't do it myself so some of this is not from experience but came up in my research.
The 2.4 has higher quality internals (forged, not cast) than a 2.2 so I think it's worth the extra bucks. somebody else can speak to that better than I.
There is no intake manifold for a single carb that will fit the 2.2 or 2.4 head (the exhaust manifold/header is different also). That is why people use 1.9 and 2.0 heads. You can get dual side draft manifolds for 2.2 and 2.4 though.
Mine has a 2.2 head and Jetronic-LE (I think) injection. Jetronic-L fits 1.9 and 2.0 heads. I was told that Motronic Injection is too tall to fit under the hood without changing from stock hood.
Pretty much everything from the 1.9 will bolt to the bigger blocks but you will probably need a better radiator and a stronger transmission. You should get a bigger clutch and flywheel also(and brakes!).
The 2.2 and 2.4 clutchs are kinda pricey so you may want to research the S-10 clutch mod.
I was told the four speed wouldn't stand up to the extra power so I got a Getrag 5-sp also. That required a modified driveshaft and linkage.
I love the car the way it is but in hindsight if I were doing it again, I would have used a nice 2.0 head with a twin 38 Weber carb. It would have been less effort/cost. The injection is smooth though! Good Luck!