I was a dumbass on disassembly and didn't take pictures. I lost track of the ordering of the main caps on the engine.

The rear cap is obvious, since it has a recessed step for the thrust bearing. How do I figure out where the other caps go?

 

Become a home schooled forensic analyst real fast. If you take real close zoomed photos of the Crankshaft Journals - and the bearing surfaces inside the three journal caps --- you 'should' be able to identify which one came from where by analyzing the slight grove counts, depths, and spacing.

Sorry & good luck.

 

You might be able to figure it out by using plastigage to check the bearing clearances. I suppose the correct way to do it is to get a machine shop to install the caps and align bore it. I had that done on a 72 455 cu in Pontiac one time. I had to replace the rear main bearing cap. I got one from a junk engine and had a machine shop align bore it to fit.