[Will]

If you're truly on a budget, you can certainly get away with reusing the stock rods at this performance level, but it may be false economy.

To make sure that a set of stock rods will live in a 400 horse engine, you will need to have them magnafluxed, resized, and install ARP rod bolts in them at a minimum. Of course, if one fails magnaflux or if the small ends have gone out of round (it happens) then you incur the additional cost of finding another rod(s).

Add up the cost of doing that vs. the cost of a quality set of forged rods, such as the new Tomahawk rods offered by Ace at PPR or a set of Scat or CAT rods. The price difference won't be more than about $100 and that's cheap for peace of mind.

As for reusing stock pistons, I'd be very surprised if you could get away with doing that. It's likely the bores in your block will need at the very minimum a hone job to restore them to roundness which will increase the clearances on those pistons by .003" or more. With all that extra clearance the pistons will rock around and bang around in the bores a lot more than a cast piston should, likely leading to failure. Just suck it up and buy a set of TRW forged .030" oversized pistons.

As mentioned, spend the money on a good short block and skimp on the heads for now. You can always replace the heads later much more easily than dealing with a blown shortblock. A good set of large valve stock heads at 9 or 9.5:1 compression will get you in the 400 horse ballpark anyway, with only a good quality valvejob on them.

6X-4 or 5C-4 are good castings to look for. Also the '69 #62 heads seem to have larger chambers than a lot of the other big valve heads rated at 10.5:1 CR. In other words, they usually come in well below their rated CR. If you can find a set of #62s that have 78cc or larger chambers in them you're in business.

Another option is to find a set of 2bbl heads from a late '60s 400 or early '70s 350. You will need to have them converted to screw-in studs and have the seats cut for larger valves but these heads (like '70 #11 castings or '69 #46 castings) have good chamber sizes for what you want to do and you can usually pick them up cheap enough to offset the cost of converting to screw in studs.

Once the engine's together, install a Crower 60242 or 60916 cam and enjoy the power!

Also, I'd recommend against the Edelbrock carb and most definitely against the Edelbrock RPM cam. I've never seen an Edelbrock carb that made as much power or got as good of mileage as a well built Q-jet and the RPM cam is simply too much cam. Don't go over about 224 @ .050" duration or you'll be unhappy with the results.

An excellent budget cam for your buildup would be the Summit 2802, though I like the Crower cam better.