Im putting a small block 350 in my s-10 blazer and i want to know if the front end will hold up to the horse power  

depends..... exactly how many horses are you planning on throwing at it? a moderatly modified small block will hold up fine in there, just be sure to beef up the welds around your engine mounting brackets to the frame.

The motor Im putting in will be making around 400 hores power.

your ganna break front end parts like crazy on an IFS....running 400 horses....if you have the money do the straight axle swap but...if you dont make sure you beef up every possible front end peice....  

I agree. either go straight axle or reconcider your engine size/HP.

is your truck a 4x4 or 2x4 and if so are you going off road? if your just going off road every now an then their want be much problems, uses some good shocks if i could figure out how to put some pictures on here i got a s-10 with almost 500 hp pluse a 175 hp shot of NOS so its around 650-675 on the bottle running a stock rearend with 31 spline axles and a GM locker 373 gears with 29" slicks that burns them up over half track.. if its a 4x4 try staying with a higher gear to cut down on the harshness..