...Doug! You're 'Half-way Home'!! How about getting a 'Short' Pump Bearing Assembly from CVF Racing Water pumps, Rebuild Kit? If the Bearing Diameter is Larger, Bore the Casting to fit. If Diameter is Smaller, turn a 'Sleeve' on the Lathe, use Locktite RED.
I want to see You Succeed!! Call them up, I'll bet they can help You! Perhaps they would be willing to Custom Build a Bearing Assembly for You, Or, Already Have One in Stock! 'Ask and Yea Shall Receive'.
When it comes to taking Measurements for Cutting the Casting Neck. I Quote..."You Better be Right Mister! You Better Be Right!!
The Shorty Pump arrives in a few hours! You will hear from Me soon.