Whats big lift? As mentioned 55 and 60MM are pretty common. If it is a wedge much harder to come by at times. Hemi/Predator stuff much asier to find as the blown alky guys use the bigger cores. IMO most any cam selection over .800 will greatly benefit from a larger than stock core, there is a surprising amount of flex with BIG lift cams and the normal big lift springs they require. Getting the block machined would be your next issues. But Weston Machine can handle it and do it right and he's in NJ so not that far away for you.