Ok fellow stovebolters, I have a theory and it might be my error. If my theory is correct.

http://i1291.photobucket.com/albums/b554/stovebolt56/2013-05-07_22-16-24_650_zpsffaaedff.jpg

The main cap on the left side is the second main cap from the rear with the "R" on it. The main cap on the right side is the second main cap from the front with the "F" on it. The bearing below was on the second main cap from the "F" on it. It looks like main cap with "R" was where it was supposed to go. However when I tried to put this bearing on the one marked "R" the second main cap from the rear it does not go on.

Could this be my problem that I but the the wrong bearing on the wrong cap?

Lastly I ahve search NAPA, Northern Auto Parts, Oriely's, and Autozone and they all say to use with the shim kit.

I do not remember any shims when I took the engine apart. Plus it appears I have a dowel at the 12oClock positions on the caps. The book says the 1956 supplement truck shop manual page 6-2 "The dowel in the upper half of the precision main bearing has been discontinued for 1956. A tang is provided at one of the butting edges of the upper new bearing. The tang which registers with a slot in the cylinder block and locates the upper bearing, also butts against the bearing cap to provent rotation of the bearing. The adjustment shims formely used between the bearing cap and cylinder block have also been discontinued. With the new tanged bearing and elimination of shims, dropping of the crankshaft in "Main Bearing Replacement" is eliminated for 1956 engines.

http://i1291.photobucket.com/albums/b554/stovebolt56/2013-05-07_22-43-51_737_zpsc223af16.jpg This is the block side of where the second main cap from the rear goes

http://i1291.photobucket.com/albums/b554/stovebolt56/2013-05-07_22-44-00_816_zps19a5cf91.jpg This is the front main cap goes.

http://i1291.photobucket.com/albums/b554/stovebolt56/2012-08-12_22-34-36_478_zpseb01f2a3.jpg this was before it was cleaned and painted but I just wanted to show the serial number on the motor 0365I39 F56X

"As I lay rubber down the street, I pray for traction I can keep, but if I spin and begin to slide, please dear God protect my sweet ride." -Amen

56 Chevy 3100