I am in a project of just those biblical proportions right now. Other than the rationalization issues and sanity considerations not to mention car strength capabilities, let's just look at the physical fittment for the time being...
I did this work on a Superformance due to the proven strength this car has shown in absorbing 700-800 and even 1000 hp along with huge doses of torque, in the past. This work was centered around a 460 Ford based block design since this is where the huge strokers are coming from, and as inexpensively and easy to to as they get.
To fit that many cubes into a block, you have to go big. The block is bigger, taller, heavier, stronger... not to mention more expensive. But when you're talking something important like your hobby, then money is no object. Just keep repeating that to yourself.
In order to get a longer crank in there, the deck needs rise like a skyscraper. As the deck goes up in height, the valve cover to hood clearance depreciates. I was able to go up no more than 2 more inches taller on the block deck in a Superformance before the heads and valve covers became an issue. Carb clearance was already an issue, but the deck did not affect it that much. Super low profile covers are needed and some really expensive "compact" valve train components were necessary. While I suppose a carb "could" stick out of the hood, I'm not so sure the valve covers should be as well.
Unfortunately, as the deck rises, it also widens at the same time. That became an issue with the Superformance steering column, which can be relocated to accomodate the larger chunk of alloy block and heads now in the way. The few folks with the 427 Cammer motors fall into a similar category.
The heads you "should" put on that engine, whcih are Arias, will not fit under the hood... so a comprimise in the best SCJ Alloy head out there will have to do. But boy, would those Arias hemi heads look good stickin out of the slots you'd have to cut into the fenders and hood for clearance! Then people would be asking you at the stop sign, "u got wun a dem himi's under yer hood?"
I've heard of 910" engines in a 460 base block, but that's about when the Tractor pull and drag orgnaizations clipped them at 650"... a mere 650 inches!!!
Anyway, with the physical limitations of the engine compartment and head clearance restrictions, you may be able to squeeze a 795" engine in under the hood if you use a dry sump
oil system, thus reducing the lower pan depth allowing the engine to sit a little lower in the frame to provide more cubic inch clearance up above.
Keeping it cheap and compact with a stock iron block (67-69-ish in vintage) sleeved, most of those can be overbored about .190" and with the same stock deck and a 4.5" stroke crank will yield you an inexpensive 585".
Next step is a Ford A460 iron block overbored .265" and a 4.5 crank giving you 605" and that's still with a stock deck height.
Then you can use the Aries A96 alloy block with a 2" taller deck, overbored .265" with a 5.5" crank to give you 738". You could get 815" from this block, but the crank arm would be getting into mythical proportions. Of course the costs would be astronomical, but hey! It's for your CAR, and hobbies have no budget, right? ... at least mine never seem to end up like they ever do.
Good luck and hope this gave some insight on the options. Just remember, to get a single motor to have nearly TWICE the cubic inches than a single stock big blocks, will certainly cost FOUR times the amount... if not more, so maybe somehere in between is where you'd want to shoot.
/Randall