Can't you stroke a 454 to a 540ci?
How about these options:
632 ci 1300 hp
Merlin or GM CNC Pro stock block, Callies / Cola 4340 crankshaft, Venolia custom pistons, Crane / Compcams custom roller camshaft, Jesel beltdrive, Jesel shaft rocker system, Fully ported Big Chief / Brodix Pontiac cylinder, 2x4 intake manifold, Holley Dominator carburetors, dry sump oiling system, MSD cranktrigger ignition, Meziere electric water pump.
Complete dynotuned motor $34900
Add $1500 for installed 500 hp Pro Race Fogger nitrous system.
730 ci 1450 hp
Tall block, raised cam, 5,300" stroke 4340 racing crank, Venolia custom pistons, Fully ported Brodix Pontiac heads with titanium valves, Jesel beltdrive, Custom roller cam, 2x4 sheet metal manifold, Holley 1250 Dominators, Dry sump oiling system, MSD crank trigger ignition, Meziere electric waterpump.
Complete dynotuned motor $43900
add $1500 for installed 500hp Pro Race Fogger nitrous system.
762 ci 1500 hp
Donovan P/S block with 1.000" raised cam, Fully Ported Symmetrical port heads with titanium valves, special shaft rocker system, Billet crankshaft, custom pistons, Jesel beltdrive, MSD crank trigger system, Dry sump oiling system, sheet metal intake manifold, split Dominators, Billet rail valve covers, Meziere electric high flow waterpump.
Complete dynotuned motor $52500
Call for nitrous oxide option