If it quit turning over as you were tightening the rod caps, start there.
I talked with my local shop about your engine and piston situation. There was no problem with the four pistons facing back wards as long as all sixteen valve reliefs were on the top side (lifter side of the bore). If you installed them with the reliefs on the exhaust side, then you have all eight rods in the wrong hole. I gave wrong information on where the valve reliefs went and apologize for the incorrect information.
The crankshaft has a radius in one corner of each rod bearing. Each rod has the bearing off set to one side for clearance of this radius. If you get the rods facing the wrong way, you are torquing the bearing down against the radius thus locking up the crank.
Pull one pair of rod caps back off and check them, if there is a sizable gap between the bearings, then you have them installed wrong. Also, when torqued down, you should be able wiggle the rods side to side slightly, if you can't, they are installed wrong.
Torquing rod bolts has no effect on rings or main bearings.
Joe
