Cast cranks can take a lot. Many of the people I race with use them and have not had any problems with their high hp engines. The bottom end in my Monza drag car consist of the following:
-cast crank(turned .010 & .010, chamfered oil holes, micro polished)
-Stock Rods (magnafluxed, beams polished, shot peened, rod & cap cut square, big end resized, ARP 190,000 psi bolts installed, weight matched, checked for alignment, and
checked for proper piston to pin clearance)
-Forged Manley Flat-top pistons
This motor makes 481 hp. I also shoot a 200hp shot of nitrous into all the time. The only part that could be considered exotic or expensive are the Manley pistons. I haven't had any problems to date and really don't think I will. Besides, I would much rather drop a valve or brake something with my low dollar cast setup than to have it happen to a high dollar forged setup.
-79 Malibu (Soon to have a fog fed 454 Big Block)
-Alston Backhalfed 76 Monza
w/1.48 60 ft (Motor Only)
w/1.40 60 ft (with nitrous, turning it off 3/4 way down the track) Should have high 9s with full nitrous run!