1.Factory oil cooler on the A2 = gaynikos said:The Honda Ep3 Si motor (k20a3) does not have oil squirters, and the oil cooler the K20A2 has.
Of course, the internals are different... different crank, pistons, rods, even bearings....
But like the B series, many engine builders remove the oil squirters so if you are planning to sleeve the K block, the A3 block could be an alternative.....
2. If you use the a3 block do not use stock internals.
3. Oil pump, pan, and water pump are different on the A2's motor.
4. A3 and A2 water passage pieces are different due to a screw so use the peice that fits.