Actually while being a bit intimidating slipping the jug over the piston is quite simple as long as you don't overtighten the clamp so that the clamp slips off the rings easy. Can't really say I've ever heard of balancing the jug with piston/rings already installed and try getting the wrist pins into the end of the piston slot but I suppose its done, guess I'm old school.

 

Putting the piston in the jug is the easiest way to do it. You have to be extra cautious with the circlip though.

 

that's the way i always do it even if the pistons don't come already installed in the bottom of the jug from a kit or something, it's a snap, real easy... trying to get the jug over an already installed piston is kinda painful in comparison.

 

clean, clean, clean! Clean everything, the cases/cylinder mating surfaces, the new bore job inside the cylinder, you dont know how clean the shop gets it., all the bolt holes and oil galleys, all mating surfaces, etc. and do not gouge anything while cleaning. Check the rockers and shafts for wear, and put the pushrods back in the same order they came out and run a wire through them to clean the oil holes. Check the lifters and cams for wear also. The pistons have a front and rear to them, so install them correctly. As front and rear, I mean a piston can be install 180 degrees out, there is a mark of some sort on the piston like an arrow on top of the piston that points to the front of the cylinder. Seat the piston pin retainers correctly and double check them. I assume that all you have done is pull the top end down? Keep it clean going together to prevent oil seepage/leaks. Lube the pistons and cylinder bores while going together, using new gaskets, torque things correctly. Its pretty straight forward, but use care. Take your time and have fun!