budget in mind,I would take the pistons out of the 454 and round up a set of dome KB pistons on the cheap around 250 bucks get the compression around 10-10.5 to 1 with your heads, go have those pressed on about another 50 bucks and new set of cast rings about 25 bucks. Hone the cylinder with a 3 bar hone.
Summit racing sells bi-metal bearings which I put in everything and you can get both rods and mains for like 30 bucks. While your at it new oil pump about 35 bucks and pick up screen another 7 bucks and tack weld the screen on, youcan get a steel sleeved oil shaft like 10 bucks at most, maybe another 10 bucks for freeze plugs. clean the crank and the block well and assemble.
Now you have a fresh bottom end on the cheap, for the cam just use a generic eddy rpm 240/246 @ .050" rpm cam- it's easy on the valve train and easy on the wallet about 100 bucks for cam and lifters make sure you find the one for 112 ls instead of the more common 114. get a new timing chain even if it's just a stock replacement or spend a little for the double roller for like 35 bucks.
So now you have a complete short block that's fresh and you have only spent, about 550 bucks.
Now the heads, have any port work done to them, just some simple casting clean up will do - meaning smooth all the casting from one end of the runner to the other end and round off the short turn, blend the bowls some and this alone is worth 5 mph in trap speed with no other changes( yes I have tested this at the track and it really does increase the trap this much for just some simple clean up on oval port heads)
The springs will have to be strong enough and retainers and all will need to clear for the .575 lift of the cam( ithink it's like .573") anyways many springs out there and I spend about 60 bucks for the needed spring thru competition products and set my seat pressure
at 110-125 lbs and over the nose 300-330 I just sort thru all the springs til I find a cheap set that will work with my install height thats around 1.88 sometimes less or more, need to know what your working with on install height, i also use new retainers and keepers and umbrella seals ( which most time come in the gasket kits about 50 bucks)
So retainers about 20 bucks, keepers another 7 and your full gasket kit for 50 bucks. springs another 60 bucks. sometimes I have to use a flat bastard to file down the tops of the guide to make room for lift on the head , to me no big deal, after I'm done I just radius the inside edge to deburr it either with a small stone or my edge knife, I just make sure it's smooth when I'm done. then clean the heads well and swab out the guides to make sure there is no trash in them and oil them.
So you are at roughly 550 plus another 137 bucks in the heads, now I like to run the 1.72 roller tip rockers so thats another 130 bucks or so. I would normally upgrade the pushrod size just because so that another expense if you want to do it, so without that upgrade your at 817 dollars.
So your at roughly 817 and your long block is done, now intake- used eddy rpm intake or air gap 100-200 bucks depends on the deal you can find, 750 or 850 holley- 750 a little cheaper I can get those on ebay all day long for under 100 bucks and throw some gaskets at it for nothing more since I have plenty of holly parts on hand. 750 set up to stock specs and running a tall yellow spring seems to work fine with this combo.
I would go with the 4.10 gears and some kind of 10" stall even if it was a cheap summit racing 2700-3000 stall that sells for $199.99 which will stall over 3k behind the bbc.
So your last amount of money depends onthe deals for the hard parts even so by my estimate 817 plus say 150 intake,100 in a carb is around 1067 in a complete ready to run bbc.
Which I have built many of these motor for under 1200 bucks. And no not because they break down, because it's simple and cheap and others see it and want one so I build for them.
With 4.10 gears and 3k stall in a th350 you will have no issue first time out to hit 12.50 @
109 mph on street tires thru full exhaust and then with some tunning and better traction with slicks open headers low 12's at 113-114 mph and more tuning and farther traction 11.80's at 115-116 mph, the combo's I have built like above is pretty much my go to build, it's cheap and easy runs on 87 octane fuel and I even lock out the distributor. shift point is 6500 on this build I use stock rods and bolts with whatever engine I'm building and all of them have been two bolt mains. I have used all sorts of head numbers on these builds, it's what ever head I have available at the time just the plain ol oval port heads.
Many hate the cam choice and say much better choices, many say the compression is to high, many say they just won't do it. But each to there own, your on a budget and this is what I do. I think this is a very detailed way of making some simple power with very little coin plus times to boot of what they can run.
Hope this helps