1 you need to read up on "how to build a motor"
2 bearing size is determined by measuring the crank and rod journals, then adding the clearance needed.There is no set number
3 Do the pistons fit in the engine with the correct clearance, again measure the piston, then the bore, add piston to wall clearance
4 crankshaft must fit the rear seal ,cant mix and match
5 measure the bore (std. .010, .020, 030 etc)and file to fit with the correct end gaps,
Take it to a good machine shop to have everything measured and they should be able to supply you with the correct parts.
