i just picked up a 1984 chevy z28 with a 350 for 1200 bucks not sure what year motor all i know it came out of truck. right now it has a edelbrock cfm carb edelbrock rpm intake comp 260 cam heddman hedders accel supercoil coil and 373 gears the tranny is a 700r4. im gonna be tearing apart the motor and building it. my goal is to get 375-400 rear wheel horse can someone tell me what ile need to accomplish this. thanks

 

Higher compression, legit heads, decent cam, then the proper carb/intake/ignition to match. That 700R4 might need a re-fresher but will take 400+ all day long. Did you want that HP to be at the crank or wheels? You'll loose about 18-25% with the trans and pulleys (usually close to 25%) Whats your emission laws where you are at? Then take it to the body shop to get it tied up.

 

With the h.p. you're after, it's not going to be a "mild" engine. Based on an average "rule of thumb" parasitic loss of 15% through the drivetrain, 400 at the wheels would put you in the neighborhood of 470 h.p. at the crank.
Your vintage 700R4 is the weaker, more failure prone one. Even the newer stronger ones in stock form won't handle anywhere near what you want, not for long anyway. So, get yours rebuilt, updated, and beefed up. Or buy one outright, you can go hog-wild if you want to: http://www.transmissionhead.com/
Next in line of needing an upgrade is your rear axle (rearend). You'd be doing well to make it into town and back before she blows apart with that engine pushing it.

 

Damn computer glitch!

 

theres no more emissions on the car and im looking for rear wheel horse

 

400 at the wheels is not realistic without going through that motor and getting the right parts to give you what you want. Random truck motors won't get the job done without a lot of work. It may have good brand name stuff on it, but if its not the appropriate cam/head/(valve job)/compression/ignition/etc. you are going to chase your own tail trying to make it right. I've agreed with just about most everything camaro69 says, but a new correctly built 4l60E (same as 700R4, just renamed and fixed for durability) will handle good hp numbers. I have a few friends that run them and have had better luck with them than anything else out there, just make sure its purpose built with the right converter, etc.

 

whatever you end up doing you have to remember you can't just end up putting a cam or single stuff like that you have to balance your engine that way your pushing same horse but it's not has hard on the engine so it will also have a longer life