I have rebuilt quite a few old John Deere two cylinder tractor engines which have shim adjusted babbited mains and rods. These engines turn about 1100 RPM and the babbit is very robust. Oil clearance spec is .003. They are full pressure lubricated engines.
I got some very good advice from the folks at Paul's Rod and Bearing about how to adjust these bearings, and I believe the same principles will apply here. Paul's specialize in rebabbiting all makes of rod and main bearings.
I also got the same advice from an old master machinist who put the crank in my 235 about 30 years ago.
It is important to polish your journals with strips of 220 grit and then 400 grit emory cloth. Go finer if you like. Scratches or pits are not going to hurt you. High spots are your problem.
The babbit can be smoothed up with double ought (00) steel wool.
Install the caps with shims and torque it up. make sure you can turn it over with no drag. Unbolt cap and remove a shim from each side. Torque it up and see if it drags. If it does, add a shim back. If it doesn't, repeat and take out another shim.
Because your crank is probably eggshaped from wear, it may only drag in two places 180 degrees apart, so be sure to rotate the engine all the way around.
The thickness of the shim you put back in after it drags is going to be pretty close to your oil clearance.
I agree that this is actually a more accurate way to adjust the bearings than using plastigage on an engine where you haven't turned the crank.
Kurt
