Step 1: Collecting up parts
Next remove the chuck and the clutch. There's a left hand thread set screw inside the chuck, then the chuck unscrews off the spindle.
For this project, all we need is the bushing, spindle, thrust bearing, set screw and the chuck. Toss the rest.
Step 2: Build a base
Mark and center-punch your holes. Two to secure the block to the table and one to hold the bearing assembly.
Start with a pilot hole.
Then drill the pilot holes out to the size of your clamping bolts. In this case 3/8".
Install the bolts permanently into the block with nuts. Use fender washers and wing nuts to clamp it down to the drill press table from beneath.
Step 3: Align block and drill for spindle.
Enlarge the hole progressively.
This bushing is 5/8" for 1/3 of its length then 11/16" for the rest. So we drill 5/8" all the way through, then 11/16" just deep enough to accomodate the wide part of the bushing plus the ball bearings and races. Be sure to measure yours as each drill may be different, even if you have two from the same manufacture.
Notice the stepped nature of the bushing.