I'm planning an engine build and I've heard the turbo style water pump is recommended but would this be illegal for a spec car? I don’t know if it was ever offered on an NA engine from the factory.

There is also an updated non-turbo pump. Should I go with this to be safe? I'm not really sure what the difference is other than the need for an additional block off plate on the turbo style.

The part #s are:

951 106 021 JX - turbo style
944 106 021 PX - updated NA

both are legal. Clearly the turbo pump needs the proper block off plate, but they work.

Frankly I don't believe they are different inside. The only difference is additional port which gets blocked off for the NA.

Yes, the front block off piece for the N/A cars is white and the same piece for the turbo's is black and water can pass thru it!