I did not include photos
I use just words here to describe how I recently described this in a Facebook forum after getting a private message to ‘describe’ the process
It is a thinking and envisioning pathway. It is not the be all end all discussion that hopefully frames the discussion and captures the variables that (can) be in play based on vintage and components present you have to work with.
Excellent upgrade. One word of hesitation as there is some diversity in what folks have.
What if the original casters stem length was just a tad shorter than the new stem lengths? Some but not all have been through the years.
Next, what if the bored lift mechanism depth that the stem resides in was not as deeply bored?
Some vary. Old vs Mid vs Later vs Present vintage assembly. With millions made over decades by varying vendors of Shopsmith, it’s easy to see slightly variant components can introduce an issue for your specific upgrade.
That said, take some time to measure what you have before you drill holes.
*If your original casters aren’t bent over or deformed*
Example: using your original casters, fully seated:
1 - lift it to first step. Measure your floor clearance at each corner and record it.
Now go to the second position and record those.
Suspend (securely) your unit on 2x4 stack and pop out original casters.
Measure stem length old vs new.
Insert the new casters and seat them.
Do they reach the plungers frame or do they sit just off the frame with a gap revealing the stem above the swivel?
Technically the plunger frame should sit on the top of the ball bearing top plate.
Original casters did not have that ball bearing swivel plate.
Yes you could fill the gap with fender washers where the visible stem exists and allow it to sit on that plate. It would solve that problem. (You May or May not have it)
Yes, you could disassemble the plunger and machine the hole deeper (I did not say drill. It is hardened)
Yes you could grind down the stem on the new casters, maintaining the rounded profile and polish them smooth allowing them to bottom out.
If you modify anything described above, remeasure after changes.
The measurements you took earlier comparing new heights to old should be considered.
It tells you how much higher the lift is going to be.
You won’t be a happy camper if after drilling and installing new casters, if your Shopsmith legs do not reach the floor and stabilize the machine to use safely.
If you consider the holes existing position and draw a level horizon line through them as the base line, and your lift and clearance worked before, creating another level horizon line at the lift difference measured should be the plane the new holes should be.
The exact location on the plane would be intersection of a line drawn between the centerline of the existing two holes.
Is that where your drilling template suggests?
If not reconsider things before you drill.
That’s my two cents.., ok my $1.75...