What was the clearance on the main cap/bearing (as read by the plastiGuage)?
When you test fit the front bearing did you have the bottom halves of the other bearings in? If not your crank could have gotten cocked ever so slightly and just enough to lock the crank down.
When test fitting the crank it's best not to install the rear oil seal as it will tighten things up enough to make it very hard to hand turn the crank.
Install all main bearings but don't torque them all down, the idea is to try to true the crank up as mush as possible for the fitting/measurements.
Do one at a time checking the clearance and the ability of the crank to turn.
If you had 2ea shims on each main bearing cap do your preliminary fitting with both installed and adjust/remove shims to get your clearance right if/when necessary.
Good luck
Dave
