These engines are exactly the same save for the center 3 mains being 4 bolts on the 283 engine.
These engines are the basis of the 350HO 330hp crate, they just take these longblocks, strip out the roller cam, pushrods, roller lifters and drop in a 212║/222║ flat tappet cam and add a Vortec carb intake.
These are also teh basis for the Ramjet 350. They remove the stock 191║/196║ 0.412/0.428" 111║ LSA roller cam, add the HT 383/Ramjet 350/Marine roller cam that has 196║/206║ 0.413"0.451" 109║LSA roller cam, add 1.6:1 roller rockers, and throw on the Ramjet fuel injection.
The 282 and 283 L31's have nodular iron cranks, frged PM rods and hypereutectic pistons topped off with the highest flowing production GEN 1 heads GM ever installed on a production vehicle.
these engines are rated at 255 sae net hp@4600rpm/330 sae net lb/ft torque @ 2800rpm, but actually output around 310 gross hp.
1/2 and 3/4 ton vehicles that had under 8600gvrw got the 2 bolt L31, and 3/4 ton and 1 ton vehicles with over 8600gvrw rating got the 4 bolt.
There is also a 3rd L31 variant p/n 12569010, it has 4 bolt mains and lists at $4600, can be had for $3809. Its almost twice teh price of either the 2 blt and 4 bolt L31 engines. Its used in the W4500 trucks. Because of the price I wonder what goodies it has inside?
For the money you might as well get the 293 with the 4 bolt mains. These engines also come with a small windage tray as well.