I am kind of new to the game and i am always seeking knowledge. After massive amounts of front end work on a 9c1 94 chevy caprice classic 5.7l lt1 350 all was good and wham the diff blows out. There was no massive increase in horse power torque ect so why why did it go? how could changes to the front end have such an ugly effect on the rear end  

When ya gotta go, ya gotta ***
Sure wish i had the answer to your mechanical failure, but there is really no way to tell w/o visually inspecting the drivetrain...  

a police version is usually well used before civilians get to purchase one. it has enough miles that you rebuilt the front end so i'll guess this is the case.
did you go through the rearend or have it looked at some point in time? police cars get abused pretty hard while in service so that rear differential may have been on it's last legs when you were trying out the improved handling after the front end rebuild. it could have failed from worn bearings, gears, or the lubricant was too low.
if you haven't increased the performance of the powerplant much, rebuild or replace it to it,s original specs. most cop cars were fitted with heavy-duty parts and should hold up to what the car is capable of in stock trim. if you plan on enhancing performance, the 10-bolt you have, won't hold up for very long and it is time to upgrade.  

Which 10 bolt came in those cars?I run a 8.5 10 bolt and my 700hp and slicks ain't hurt it.Stock axles,too.  

my literature shows it as having the light-duty 10 bolt, the ring gear is only 7.625" in diameter. not real durable for much more than stock. mine broke at about 350 hp.