I am adding all this up in my head, and figure the best way to go with something like this is a 351c block, LS6 heads, and LSx truck intake.
The 351c has nearly the same deck height, so you can use a stock intake.
The truck intake is known to be the best stocker out there for the LSx.
The speed guys just can't take advantage of it because it is so tall.
That leads me to the next point...
The tall intake on the trucks is very similar in design to the 5.0 Stang intake.
No interference with the distributor! Unlike the car intake that has the TB over the water pump.
There are PLENTY of aftermarket controllers for the LSx out there, and there even would be ways to make the stock harness and ECM work.
Also, I don't see a big deal in getting the cam made.
The lobes don't care if they are working intake or exhaust.
If you keep it simple and use a single pattern cam, it shouldn't matter.
Edit:
I just thought of another big plus for using the C block!
The water outlet in the block... no need to rig up hoses to the freeze plugs like the poster on the other forum was contemplating.
Edit2:
Heck with it...
Now that we got the intake fitment figured out, just get a carb intake for the LSx and put it on the Cleveland. Don't even worry about the ECM!
Maybe not though... EFI is one of the components that makes the LSx engines so good.
Tough call.
Why not just put a 5.0 ECM in there? Should work.