i want to rebuild my small block (or a new one if necessary) to put out about 400hp at the wheels. i'm driving all day, everyday, so reliability is a must. i've recently installed a holley 670cfm street avenger and a 700r4 transmission. what type of things should i plan for my block?

There is no replacement for displacent --- ESPECIALLY when you are talking about a daily driver. I would start with a 400 block or a 383 if you can afford to build a stroker. Torque rules on the street so keep the cam and heads reasonably sized, same with the carb (your 670 is nice).

Just some general ideas. Can only get more specific if you give more info, like how much you can spend and how is the chassis set up now (gears, stall, etc.). And of course how fast do you need to go? You might be able to reach your goals with a 350 or even smaller if you are concerned about mileage and cost.

What engine do you have in the car now?

well i bought the car a few years ago. it had the orignal powerglide in it, but the 327 had been replaced somewhere down the line with a 350, not a supersport. the only thing the guy who sold me the car said was that it had camel heads and an rv cam.

as soon as i got the car i parked it and pulled the block. i cleaned out the engine compartment, replaced the bushing, brakes, alternator, battery, things like that and rebuilt the heads, but i have never opened up the block. the tranny went out last year, so i replace it with the 700r4 the first gear, a 3.06 and if i remember correctly the stall is at 2000. the carb i had a small fuel leak, so i replaced it with the 670 holley.

im planning on spending anywhere from 3-6 grand to get the engine to where it needs to be in order for me to be able to drive it and not have to worry about getting stranded.

the car is pretty much stock all the way around. this summer im also planning on converting to disk brakes in the front and upgrading the suspension.

Saw a 396 crate motor on ebay for about what you want to spend.

OK, here's how I do it if it were my money (assuming of course that the engine bottom end needs to be redone):

Reliability helpers:

New Accell HEI distributor $125
New (Powermaster?) High TQ starter $125
New Stewart aluminum water pump $160
New stock radiator $180
New hoses and belts $100

Fun stuff to go fast reliably:

Block machine work (bore, line hone, deck) $750
New Eagle cast stroker kit (SIR Rods, KB -18cc pistons, bearings, rings, dampener, flexplate, etc) $1000
New 180cc Pro Topline Iron heads with 72cc chambers $750
Edelbrock Performer RPM intake $120
Comp Cams XE262 & lifters $160
Comp Magnum 1.52:1 Roller tip rockers $100
Felpro gasket kit $120
New pushrods (get decent quality moly steel ones $65

That adds up to about $3800 if you assemble it yourself and should make enough TQ on cheap gas to spin the tires whenever you like while getting decent mileage and being stone cold reliable. Desktop Dyno says 372 HP @ 5000 RPM and 415 ft/lbs TQ @ 4000 RPM with 382 ft/lbs down low at only 2000 RPM.

Just my opinion.