I just brought home my used 350 short block Targetmaster motor. Ive started disassembling it and so far everything looks really good. I will be taking the block and crank to the machine soon. What are the basics i should have done and what are some other performance things i can have done while everything is there. Is blueprinting/balancing worth it ? Im looking to get about 400 horse out of it or possibly make it a 383 if i can find a cheap enough 400 crank.

I have heard good things about SCAT cranks, maybe if you really want a 383 you should give them a try. Balancing is Definately a good idea!
So are longer rods if you can afford to go that far or are planning to replace the rods anyway. Check out David Vizard's books on building a small block chevy. I also found some other books helpful so go to your bookstore or see classic motor books online to see what is available! Getting the knowledge these guys spent years gathering and thousands of dollars spent in testing for $20-30 is well worth it.
Have fun!

BLASTER
AFTER THE BLOCK IS CLEANED AND MAGED AND MAYBE A SONIC TEST ON THE CYLINDERS IF ALL THATS GOOD, I WOULD START WITH A LINE HONE WITH A PERFORMANCE MAIN BOLT KIT,SQUARE AND DECK TO 0,BORE AND TOURQUE PLATE HONE AND BALANCING IS A MUST.