Ok, here we go !
This is a picture of one of the 2500 J2's produced between the years of '57 and '58;
These were all known as Golden Rockets. It was a $83.00 option. As you can see, there are no dimples on this J2 motor.
Now, out of these 2500 J2's very few were the competition motor with the heavy duty internals and radical cam, recommended for competition and off road use. It was a $385.00 option. [ in 1957 !] I have been told the competition motor was the one used in this Oldsmobile add;
Now, that doesn't mean that you have the competition motor, as someone might have simply changed them out.
So, I want you to re-check the number on your intake manifold. If it is still 571175, then I would say you have the competition motor. Oldsmobile lists 571145 as the 'normal', but still rare, J2 !
I have not been able to confirm anything on the raised W2 stamped on the intake yet. But, I can't find that same stamp on a 'normal' J2. I am still searching my archives in my attic to find some more information on your engine number. The vin number is XXXXX states you have a 1957,88,with a 371.