V6 upgrade problem
 

My friend has a V6 3.8 in a 1995 Mustang. He bought an engine kit for a F150 4.2 I belive. Has anyone else done this because the pistons and rods fitted fine but with the crank and the bearings the engine would not turn. We put the stock crank in and a set of stock bearings from the 4.2 and it rotates just fine now. Has anyone else done and have had problems.