I wouldnt know of a specific number to put on it, but I would invest a new driveshaft with ujoints. I put alot of passes on my stock driveshaft running mid 11's and anywhere from 2.0 60's when first starting with the car to 1.4 60's til it finally broke. Not that expensive for piece of mind, I paid $380 for a steel 3" with brute force ujoints and a forged front slip yoke after a mishap at Norwalk a few years ago. Cut a 1.42 60ft approx 100ft or so out the rear yoke/ujoint mount sheared off rearend. I lucked out it didnt come thru the floor pans. It will break eventually and your better off just upgrading it rather than waiting for it to break and cause other damage to the car or yourself.