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My GE coded T4 has a square port exhaust head on the port side and an oval port head on the starboard. Somehow this doesn't seem normal.
According to Google AI the 1978 GE coded engine had oval ports and the 1979 had square.

No shortage of fools to do wackmo things to these engines over the last 40 years or so…

Next question. Which head is the better head, oval port or square port?

Oval ports easier to source, and have less port to absorb heat from in the head.
If you actually have good heads to rebuild, run what you got. (somewhat unlikely, but possible)

if I was building a ~stock bus engine I would find some 1.7l 914 heads to rebuild, as they are probably in far better shape (not as overcooked) than late bay bus or vanagon heads, and flow better, same size valves.

The heads, both kinds, are available new in decent quality.

Heat exchangers, not so much.
The Aftermarket new Dansk don’t have the fine construction of the original German.
These OG exchangers are getting heard to find as they’re prone to rust.

i’d vote for new oval port heads and an OG heat exchanger if the choice was mine.

Used Bus heads are rarely worth rebuilding.
The pulled stud i see in your pic isn’t a good sign.


JMHO..

So I scored a complete GD coded Type 4 with cylinder heads and a set of 96mm Porsche cylinders and pistons. My original GE coded type 4 should be rebuilt soon with matching heads.

For the GD coded type 4, will the Porsche jugs and pistons fit without replacing the crankshaft?

Yes, assuming the "Porsche" cylinders are for a 2l t4, and assuming no one popped a 1.8l crank and rods in a 2l block, and that the cam is ok and. the heads aren't a maze of tiny cracks behind the exhaust seats.
(the ~50 year old original heads are very frequently toast, thus the previous suggestions of new heads)

If they are flat top 914 pistons by some chance, your compression ratio will be way to high for a bus or any near stock cam.
Good for a hot cam in a light car.

2L 914 heads have 65cc open chambers, bus heads have bathtub chambers ~55cc.
2L bus engines also have 12cc dishes in the pistons so the actual chamber volume is not hugely different, but mix and match parts can get interesting.