You can go really inexpensive if 800 is really where you want to be. Going forced will pile the dollars on right along with the power. To save every buck you can here's what I'd do.

Scat 4.5 crank
H beam 7.1 rod
11.5:1 piston from any of the big companies with a standard 1/16 1/16 3/16 moly ring package
SV replacement head with basic port work (bowls-port entry stuff) stainless valves
Indy roller rockers on steel stands
mega, or world block Iron. Move the pickup over and use 5/8 pickup, keep it internal for cost.
solid flat tappet with chain drive
Indy small plenum 4500 single 4
OTB holley 1050
steel tray and milodon pan

It'll make over 800 and be about as cheap as you can go. Going forced means throw all that out the window and get ready to get off the hip