I run a girdle on my 340 block and I'm putting out about 625 HP on alcohol. The main caps had to be machined down where the stud nuts and washers set, this way I didn't have to shim to get the girdle to fit evenly across all the main caps. Been running it hard for 6 seasons and the main bearing look like new. Running 6.50 sec. to 6.67's at 101 - 102 mph depending on the air, tune and traction.