My rebuilt 4AGE is going  to be ready in a couple of months to go in my KE20 and I need to start thinking about headers and an exhaust.

Looking for ideas of what would fit off the shelf for headers down to the collector. Engine is not in car but need to get headers sorted at least if feasible.

Anyone able to offer any suggestions?

Unless someone has done that conversion into a KE20 you'll have to measure it up with the motor in. I used the stock RWD manifold and made up the pipes going from two to one under the floor. Doing it cheap, I even bought a good exhaust system off a VL Commodore at the wreckers and cut it up to remake it into the shape I needed.

https://www.rollaclub.com/board/topic/42407-the-girls-ke70/page/10/#comments

There are several big companies making beautiful shiny extractors for the 4AGE, sure to fit a KE70 or an AE86, but I don't know how they would fit over your steering.