Eljaro Would like to see the damage of the block. As long as the main webbing in the center of the block is not broken any aluminum block can be repaired and remachined for usage. I think that without pictures of the rest of the damage it will be hard to say if this block can be repaired. Aluminum is easier to fill, grind, and remachine that iron.
Crankshafts 101 This is from my many years of breaking parts.
Out of balance assemblies cause more breakage that anything else. Only the better machine shop TAKE the time to do a complete balance job. This includes, flywheel, crankshaft, weight of rods, pistons,rings,bearings, piston pins and a couple of grams for
oil, dampener, and even pulleys are indexed. There are a couple of companies that will custom build a dampener to get more hormanics out of the assembly for a certain rpm range. This cost from $600.00 to $1,000.00 dollars.
I think people get confused on different info on a cast, forged, and billet crank shaft. Different strengths are also in this mix too. forged crank may be just that but not a 4340 steel. Some cranks get other processes done to them to make them stronger. The problem with this is stronger the crank the more brittel it can be. A test for top of the line cranks is to hit them with a hammer and listen for the sound. IF it rings like a bell, the crank is good, if it clangs it's got a weak spot. The other issue is the rotating mass of about 100 pounds on an fe motor with small bearings both mains and rods. The larger the bearing, the more load it can take and spread out over the surface. IMO a cast crank should be limited to a 6,200 rpm max and this is once in a while not every time the car is ran. A forged crank can go to 7,500 rpms, IF everything is done to help the balancing of "0". The other side note is
oil pressure for a street motor. An FE needs a higher
oil pressure both at idle and 6,000 rpms than a GM or dodge motor. IMO idle is 30-35 psi and 65-80 psi from 2,500 rpms and up is sure life to an FE. Just like in the 60's.
As long as you get a crank forged with a good steel you should have any more problems unless you are redlighting the car and banging off a limiter when driving. Top of the line crankshafts are about $2,500.00 plus final machine work. Callie, LAE, Hank the Crank, and Velesco are the best IMO but waiting for 8-25 weeks suck. Waiting to see pictures of the parts. Rick L. Ps get a top of the line dampener also for this motor that will absorb harmonics better than a stock dampener with a rubber center. Unless rubber dampener is pinned it can spin out of balance and break the crank also same with pulleys that don't spin true.