oh geeze....
Anywho... 250 build:
Offy intake: $200-ish
Holley 390 CFM carb: $100 + rebuild or $300 or so.
Langdon headers: $300
Exhaust: Figure another $500 or so.
HEI: You can get them cheap on Fleabay for under $100 or go with a nice one for $300.
Cam swap: $500 or so (figure cam, springs, lifters, gaskets)
Radiator and electric fan (frees up 15-20 hp): $200 cheap or up to $1000 for something that won't do much more than the $200 setup will
2004r trans swap: Figure anywhere from $500 to $2,000 depending on how far you go there.
Rear-end gears and posi: $600 if you do it yourself.
Lumps and oversized valves: $800 or so
That'll scoot you down the road pretty well. It'll be like having a stock 350 and with the right gears and trans you'll knock down some decent mileage too (I'm guessing in the 20's). You'll be around 250-275 hp and have the gearing to use it properly.
You'll run into a lot of "while I'm in there's" so add 10% to your budget. Also this is assuming you do the work yourself. You can go a step further and do pistons and rods and have it ready to turbo charge it to hit around 350hp or so or just keep the boost lower and hit 325hp with stock internals. If you do that I recommend EFI and water or meth injection to stop detonation.
Here's what mine looks like right now not 40 feet from where I sit:
(plug wires, distributor and battery are out)
More pics:
http://imgur.com/oSDlVcII'm in the middle of finishing up my transmission swap. I also did some other things (remember when I said "while I'm in there's?"...). That project is in the "engine pulling 101" thread in this forum.
I haven't done the rear end or head work yet. Doing mine in stages. Also no internals at this time either. I probably have 3 grand in the engine spread out over 4 years so it's not too hard on the wallet.
