In what order does the pushrods go on a 1998 Chevy Lumina 3.1?

There is no certain order. Just as long as you get the exaust pushrods with exaust vavles and intakes with intakes.
IMPORTANT: Place the valve train parts in a rack in order to ensure that they are installed in the same location from which they were removed. Intake pushrods
measure 144.18 mm (5.68 in) long. Exhaust pushrods measure 152.51 mm (6.0 in) long.

IMPORTANT: Use care when removing the pushrods. Ensure that they do not fall down into the lifter valley.

4. Remove the pushrods.