My reference sez 250 at .o50. Sheesh. These were on a 113.5 split (eaguherk!). My suggie is buy the Isky .560' Z-11' grind that's on a 110 split core. Big difference the split makes. My brother bought the old Crane Z-11 copy for his '58 and it was a dog with 3.36 gears and a 4 speed. The 4.11 swap helped a bit (no Posi so I doubled the spider shims for a semigrip), but a 113.5 split? Rechhhhh! Might as well drive a small block with AC and a Powerslide.........on second thought, just get it over with and buy a bus ticket......
The wide split helps the vacuum as well as the idle.