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Having run a blown small block street/strip since 1985 I'll put in my 2 cents. Mine is a 340 so not everything applies. Stock block was used over 20 years, no failure. Upgraded to a R-3 block a few years ago. The result is less blow by,the breathers never drip a drip now. Original stock crank, rods were from the Chrysler Trans Am program. Venolia forged piston( 5/64 moly rings). I have beat on this thing to 7000 rpm a long time. Carb's were very rich a one time,not now. Stock jetted Carter Comp 750's, A?F is still 11.8-1 at wot. Timing is the key. Destroyed 2 sets of pistons before I figured that out. Only30 degress total lead. Same pistons since 1991. I run 12 PSI. Car runs [Email]11.0@123[/Email] 3875lbs in street trim.
Doug

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Classic example of what works and what doesn't. Just remember thought RB bottom ends ARE sturdy for most forms of competition, but emmense loads of torque/hp can play havoc with them. RB crank rod assemblies being both larger in stroke and rod length, exhibit more stress loading than it's B engine counterpart. B engine bottom ends are blessed (like the 340) with smaller circumferenced
cranks (less stress and rod loading). The 340 main webs are a bit thicker than the B/RB's main webs (even though the mains are nearly encased inside the B/RB motor). Bobweight and balancing, plays a big role too. The more mass to spin, the more power it soaks up. RB assemblies are heavy (in standard form) to begin with. Although VERY strong, they are high-torque, moderate hp/rpm pieces, with a some exceptions due to engine options.
Again it boils back to building a SOLID foundation
(a properly machined, clearanced and balanced block assembly), with a proper selection of power-producing parts/equipment, up top. By the way, Trans-Am engine pieces are kinda rare these days and were of the "improved" versions of the 340 hi-po production pieces. A much different forging than 340 Magnum pieces, they were made to take high stress loading at 8K, maybe higher in rpm. 3875lbs, not bad! Shed 300-500lbs and do some tuning, 10-teens are easy!