Nope- it won't work. The old Schwinn one-piece cranks don't have enough material to allow them to be drilled & tapped for 9/16" thread pedals.

It's possible to replace the cranks with a conversion bottom bracket and 3-piece cranks, but the chainring on the old Schwinn Exercisers was huge- something like 60 teeth. These are available for recumbents and downhill bikes, but it's a pricey proposition.