I recently re-built my 350 in my Blazer. I had it all balanced. There was a problem with the rear main seal so crank, cam and all of the bearings got ruined after only 10 miles. My question is when I get my new crank do I need to rebalance the whole rotating assembly or can I get away with just rebalancing the crank?

 

which ever Shop did your engine balancing before...should have your balance record on computer or index card

you should get a price break..because all they have to do is balance the crank...from your original Bobweights

you paid already for them to establish your Bobweights

so it should require less time/effort to balance your crank to that Bobweight as long as 2 cranks are identical in manufacturer/alloy/application