The barrels will work.... sort of. You may see some restricted flow at four of the oil returns through the F2 barrels. The F2/F3 only used four oil returns while the early K barrels used eight:
Also, I believe the F2 pistons had a higher dome since the F2 heads used a taller combustion chamber. You would need to verify clearance between the F2 pistons and the K3 head.