Your narrative is a little confusing. The thrust bearing on a 235 is the #3 bearing, not the "rear" bearing at the flywheel. The rear bearing has four bolts, while #1,2,and 3 have two bolts each. By reading between the lines (which often leads one to incorrect conclusions) it seems that it's possible the bearing bores are slightly out of alignment.
Personally, I detest Plastigauge. I set bearing clearance by sandwiching a narrow strip of shim stock between the lower bearing shell and the crankshaft, and add or remove shims between the cap and the block until the desired amount of drag on the shaft is achieved. A firm pull on the flywheel which achieves a smooth rotation of the crankshaft is my goal. I use a .0015" strip of shim stock about 1/4" wide as a setting gauge, and adjust shims as necessary. Sometimes it's necessary to "split" shims- - - -one less layer on one side of the cap than the other, usually a difference of .0005" side to side. Once the desired drag is achieved, remove the checking shim and proceed to the next bearing. Do the clearance setting BEFORE fitting the rope oil seal! Obviously, the crankshaft must be round, and with little to no taper wear front to rear to get a good clearance adjustment.
On the Babbit rod 216 and 235 engines, the connecting rod clearance is set the same way- - - -use a .0015" check shim, and adjust the rod to cap shims the same way. Rods can also be scrape-fitted to achieve a perfect fit to the crankshaft journals before setting the clearance, something that should not be attempted with a precision insert bearing. Good luck!
Jerry
