looking for some help on a 340 build

I'm going to have to agree with what's been said so far. You need almost twice that much to get to the 450 hp mark with a 340.

I have a complete 340 sitting on my engine stand almost ready to go into my Challenger that I believe will be solidly over the 400 hp mark (maybe not 450 though) , and I have a little over $5k into it at this point. My build looks like this

'68 340 block , .060 over, stock forged crank
Stock reconditioned rods and ARP bolts
Stock windage tray, HV oil pump, Kevko oil pan
KB 243 pistons, 9.9:1 compression with 65cc chamber and .039" gasket ( pistons are .018" over the deck, btw)
Lunati Voodoo 60404 (hydraulic flat tappet), duration 276/284 (advertised) lift .513/.533
308 heads, 2.02/1.60 valves, ported and flowing 264 cfm at .500"
Edelbrock RPM Air Gap manifold
Holley Street Avenger 770 cfm
Hooker Super Comp headers, 1 3/4"
Smith Brothers push rods
Harland Sharp roller rockers

There's a few goodies on there, but it doesn't tell the whole story. I did this with a budget in mind, and the Harland's were bought second hand (they were used as a mock up set by another member), the intake and headers were bought used. All were nearly half of new cost. I had to go with custom pushrods because of the length needed and the adjustable arms (ball/cup set-up).

And, I would do a few things different if I had to do it over. I'd go forged pistons, first of all. Nothing wrong with the hypers per say, but when I did the short block I didn't have the heads (not a good idea, btw) and I ended up doing more work to the heads and going with a bigger cam, so in retrospect I wish I had the forged pistons for piece of mind.

I would also have used RHS heads. After I bought a set of 308's, had them opened up to 2.02/1.60 and ported to flow 264 cfm @ .500", I spent more money than a set of RHS heads would cost, and flow a little less than the RHS heads would. Not entirely my fault, as the RHS heads weren't available when I bought my 308's (been at this build for too long).

My suggestion would be this. If you have to rebuild the engine right now, build a solid short block. Get forged pistons, have everything magnafluxed, bored, square decked, etc. And use a milder cam, a stock set of heads, exhaust manifolds etc. You won't make 450 hp, but you'll have a solid engine, and you can probably be close to your budget.

When you can afford to go back and spend $1,500 on heads, $700 on headers, $500 on a big carb etc you'll be able to swap in a big cam, bolt everything on and be in the ballpark for your HP goals. The only thing you'll really lose money on is the cam, I'm guessing you already have a 4 barrel manifold and carb to go with a mild 340.