what blew? I am assuming crank if it is the crank did it take out the case?
if it took out the case u will soon be under watter.
If not and it is just a melt down... it still may be a " leave it alone " deal.
My SD when burned down, had cracks starting in between the Exhaust ports and the RAVE blade slot. If you start replacing cylinders & pistons & ect.... then might as well add a PTO bearing leaking ISO.... you will be out 2k before you know it.
Just saying .... but at that point , some times a deal is not a deal ! Not to mention how many miles the sled may have and it's general condition......
Then to add injury to insult .... with my new cyl, when I did a leak down.... I still had a pressure loss, very small but was able to track in down to the perosity in the casting , leaking air , very small bubbles but enough to drive me crazy , dropping a few lbs over several minutes....
Just for the record.... I do love my SD..... not bashing here. Just stating facts for the OP to make his decision on.