The most economical would be to buy a block from Nr-racing. 1/2 the price of a new engine.
true but what if the crank journal is scored? thats another added expense, plus side cover if it's worn from the cam and crank bearing rubbing it...
a new engine will yield a spare head to play around with, extra tin to paint up, recoil ect ect..
also when you got it running did you run it easy for a few tanks of gas before romping on the throttle or did you just hammer on it right away?...
Side to side movement from the rod is normal, just as long as it's not too excessive..Look at the rod and see if there is wear on the sides, if not the rod should be fine...I would replace the bearing if it looks like it has any wierd wear marks on it or score marks..
You will notice wear on the side cover simply because the cam and crank rub the cover ever so slightly...if it's excessive you probably didn't have any end play on the crank and should have maybe doubled up on the cover gaskets...I had to do that on my clones....some gaskets made by different companys are different thicknesses, you wouldn't notice it much until the cover was bolted down and you checked your end play.....On 5hp briggs flatheads they sell cover gaskets in various thicknesses to set the end play on the crank...
I set my end play so I can just get a little movement but not slap the crank back and forth....Others may have different oppinions on doing this...It should be done with a dial indicator to spec I suppose but this method has never let me down to date...
No end play will cause premature wear and failure...